- Highly selective and recyclable MoO3 nanoparticles in epoxidation catalysis
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Molybdenum trioxide (MoO3) nanoparticles with an average size below 100 nm were prepared by solvothermal synthesis of nano-crystalline molybdenum dioxide (MoO2) and subsequent thermal oxidative annealing. The successful preparation of this type of nanoparticles was confirmed by evidence obtained from characterization by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) analysis and Fourier transform infrared spectroscopy (FTIR). The MoO3 nanoparticles were tested as catalytic precursor in the epoxidation of cis-cyclooctene, styrene, R-(+)-limonene and trans-hex-2-en-1-ol, using tert-butylhydroperoxide (tbhp) as oxygen source under different reaction conditions, namely, various solvents and temperatures. The catalytic studies show that the MoO3 nanoparticles perform selective epoxidation of the tested substrates with very high yield, especially at high temperature and using toluene as solvent. Furthermore, the catalyst remains active across several reaction cycles with virtually no loss of activity.
- Fernandes, Cristina I.,Capelli, Silvia C.,Vaz, Pedro D.,Nunes, Carla D.
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- Monovacant polyoxometalates incorporated into MIL-101(Cr): Novel heterogeneous catalysts for liquid phase oxidation
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Two novel hybrid composite materials, PW11@MIL-101 and SiW 11@MIL-101, were prepared by the inclusion of the potassium salts of the monovacant polyoxotungstates, [PW11O39]7- (PW11) and [SiW11O39]8- (SiW 11), into the porous Metal-Organic Framework MIL-101(Cr). Materials were characterized by a myriad of solid-state methods such as powder X-ray diffraction (XRD), vibrational (FT-IR and FT-Raman) and 31P solid-state NMR spectroscopies, elemental analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), and textural analysis confirming the incorporation of the POMs into MIL-101(Cr). PW 11@MIL-101 and SiW11@MIL-101 revealed to be active, selective and recyclable catalysts for the oxidation of cis-cyclooctene, geraniol and R-(+)-limonene using the H2O2 as oxidant. Only one product was obtained from the epoxidation of cis-cyclooctene and geraniol: 1,2-epoxycylooctane and 2,3-epoxygeraniol, respectively. In the oxidation of R-(+)-limonene the main products were limonene-1,2-epoxide and limonene-1,2-diol, however the diepoxide was also formed. Both composite materials, PW11@MIL-101 and SiW11@MIL-101, are recyclable for, at least, three consecutive cycles without significant loss of activity. The stability of the composites after the catalytic cycles was confirmed by several techniques. Remarkably, the MOF framework was found to play an important role in the stability of the PW11 in the presence of H 2O2.
- Granadeiro, Carlos M.,Barbosa, André D.S.,Silva, Patrícia,Paz, Filipe A. Almeida,Saini, Vipin K.,Pires, Jo?o,De Castro, Baltazar,Balula, Salete S.,Cunha-Silva, Luís
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- Hydrogen-peroxide epoxidation of natural olefins catalyzed by a dinuclear manganese complex
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The complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L) [L2Mn2O 3](PF6)2 catalyzes epoxidation of (+)-limonene in CH3CN solution at room temperature. Adding CH3COOH accelerates the reaction. The products are isomers of limonene epoxide with predominance of that with an epoxified ring double bond. Epoxidation of α- and β-pinene by this system is less effective, apparently due to extensive steric shielding of the double bonds in the pinenes.
- Mandelli,Voitiski,Schuchardt,Shul'pin
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- [Mn(TPPS)] immobilized on ionic liquid-modified silica as a heterogeneous and reusable catalyst for epoxidation of alkenes with NaIO4 under ultrasonic irradiation
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Effective epoxidation of alkenes using sodium periodate was accomplished with Manganese (III) tetrakis(p-sulfonatophenyl)porphyrin, [C44H26N4O12S4Na4], supported on ionic liquids-modified silica, Im-SiO2, under ultrasonic irradiation conditions is reported. This heterogeneous catalyst, [Mn(TPPS)@SiO2-Im] was characterized by elemental analysis, scanning electron microscopy (SEM), FT-IR and UV–Vis spectroscopic methods. The synthesized hybrid catalyst was applied for efficient epoxidation of various alkenes with sodium periodate in acetonitrile under ultrasonic irradiation conditions. This solid catalyst can be easily recovered by simple filtration and reused several time without apparent loss of its catalytic activity.
- Hajian, Robabeh,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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- Fluorinated alcohols: Effective solvents for uncatalysed epoxidations with aqueous hydrogen peroxide
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Buffered aqueous hydrogen peroxide in combination with fluorinated alcohols (trifluoroethanol at reflux temperature or hexafluoro-2-propanol at room temperature) oxidises a variety of alkenes to the corresponding epoxides in high rates and fairly high yields, without the need for any catalyst.
- Van Vliet,Arends,Sheldon
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- Eco-friendly solvents and amphiphilic catalytic polyoxometalate nanoparticles: A winning combination for olefin epoxidation
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Eighteen eco-friendly solvents were examined to carry out the epoxidation of olefins with the amphiphilic catalytic dodecyltrimethylammonium polyoxometalate nanoparticles [C12]3[PW12O 40] in comparison with [H]3[PW12O40] and [Na]3[PW12O40]. Surprisingly, the screening of solvents with cyclooctene has revealed that the [C 12]3[PW12O40] catalyst is much more active with initial turn-over frequencies, TOF0, increasing up to a factor of 10. Moreover, the reaction occurs at competitive rates in four relevant solvents, i.e. cyclopentyl methyl ether, 2-methyl tetrahydrofuran, methyl acetate and glycerol triacetate, for which TOF0 values are higher than 260 h-1. The recyclability of the systems is demonstrated and the scope of substrates has been successfully extended to cyclohexene, 1-octene, limonene, 3-carene, α-pinene, β-pinene and neryl acetate with good epoxide selectivity. The catalytic performances in the "green" solvent are assigned to the formation of stable [C 12]3[PW12O40] nanoparticle dispersions which have been characterized by transmission electron microscopy and dynamic and multiple light scattering experiments. Finally, the Kamlet-Taft parameters were measured in order to correlate the physicochemical properties of the solvents and the catalytic activity.
- Mouret, Adrien,Leclercq, Loic,Muehlbauer, Andrea,Nardello-Rataj, Veronique
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- Vanadyl cationic complexes as catalysts in olefin oxidation
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Three new mononuclear oxovanadium(iv) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol-1V h-1) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol-1V h-1) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal CC bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)]+ (1+) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(iv) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)]+ complex is the likely active V(iv) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium. This journal is
- Nunes, Carla D.,Vaz, Pedro D.,Félix, Vítor,Veiros, Luis F.,Moniz, Tania,Rangel, Maria,Realista, Sara,Mourato, Ana C.,Calhorda, Maria José
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- Perfluoroheptadecan-9-one: A selective and reusable catalyst for epoxidations with hydrogen peroxide
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Perfluoroheptadecan-9-one is a selective and mild catalyst for the epoxidation of a wide variety of alkenes with hydrogen peroxide; after the reaction the catalyst can be easily recovered and reused without noticable decomposition.
- Van Vliet, Michiel C. A.,Arends, Isabel W. C. E.,Sheldon, Roger A.
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- Continuous flow photooxygenation of monoterpenes
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Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
- Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
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- Titanosilsesquioxane anchored on mesoporous silicas: A novel approach for the preparation of heterogeneous catalysts for selective oxidations
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Ti-polyhedral oligomeric silsesquioxanes (Ti-POSS) based heterogeneous catalysts were prepared by anchoring of a functional titanium-containing silsesquioxane on the surface of an ordered mesoporous silica (SBA-15) and a non-ordered silica (SiO2-Dav). The anchoring process was followed by IR spectroscopy, which leads to the condensation reactions between surface silanols of silicas and ethoxy groups. The heterogeneous character of catalysts checked by removing the solid catalyst by centrifugation and testing the residual liquid mixture show no significant loss of active species. Anchored heterogeneous catalysts show lower conversions with respect to reference materials prepared by direct grafting of titanocene on the same silica supports. It is also seen that the anchored materials display slightly better results than those obtained over reference titanium-silica catalysts with comparable metal loading.
- Carniato, Fabio,Bisio, Chiara,Boccaleri, Enrico,Guidotti, Matteo,Gavrilova, Elena,Marchese, Leonardo
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- Remarkable axial ligand effect on regioselectivity towards terminal alkenes in epoxidation of dienes by a robust manganese porphyrin
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With a highly encumbered manganese porphyrin as catalyst, significant improvements in regioselectivity towards less substituted C-C double bond in diene epoxidation were attained by simply adding organic bases as axial ligand.
- Lai, Tat-Shing,Lee, Stephen K. S.,Yeung, Lam-Lung,Liu, Hai-Yang,Williams, Ian D.,Chang, Chi K.
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- Spectroscopic, calorimetric, and catalytic evidences of hydrophobicity on Ti-MCM-41 silylated materials for olefin epoxidations
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Hydrophobic Ti-MCM-41 samples prepared by post-synthesis silylation treatment demonstrate to be highly active and selective catalysts in olefins epoxidation by using organic hydroperoxides as oxidizing agents in liquid phase reaction systems. Epoxide yields show important enhancements with increased silylation degrees of the Ti-mesoporous samples. Catalytic studies are combined and correlated with spectroscopic techniques (e.g. XRD, XANES, UV-Visible, 29Si MAS-NMR) and calorimetric measurements to better understand the changes in the surface chemistry of Ti-MCM-41 samples due to the post-synthesis silylation treatment and to ascertain the role of these trimethylsilyl groups incorporated in olefin epoxidation. In such manner, the effect of the organic moieties on solids, and both water and glycol molecules contents on the catalytic activity and selectivity are analyzed in detail. Results show that the hydrophobicity level of the samples is responsible for the decrease in water adsorption and, consequently, the negligible formation of the non-desired glycol during the catalytic process. Thus, catalyst deactivation by glycol poisoning of Ti active sites is greatly diminished, this increasing catalyst stability and leading to practically quantitative production of the corresponding epoxide. The extended use of these hydrophobic Ti-MCM-41 catalysts together with organic hydroperoxides for the highly efficient and selective epoxidation of natural terpenes is also exemplified.
- Silvestre-Alberó, Joaquín,Domine, Marcelo E.,Jordá, José L.,Navarro, María T.,Rey, Fernando,Rodríguez-Reinoso, Francisco,Corma, Avelino
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- Lipase-mediated epoxidation of the cyclic monoterpene limonene to limonene oxide and limonene dioxide
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Limonene is an industrially interesting monoterpene that accumulates in bulk quantities as byproduct of the fruit juice industry. The corresponding epoxides are versatile synthetic intermediates and additives for the chemical industry. Due to a number of disadvantages of classical chemical epoxidation including serious safety issues and unwanted side-reactions, we here used a mild lipasecatalyzed chemo-enzymatic epoxidation system, with either free or different immobilized forms of Candida antarctica lipase B. Full limonene conversion (° 98%) was easily achieved at 40°C within less than 24 h. The enzymatic activities in the formation of limonene monoxide significantly varied from either 1-3.4 U/mgbiocatalyst at r.t. or from 1.7-4.9 U/mgbiocatalyst at 40°C. For the first time we showed that it is possible to generate high amounts of limonene dioxide (～ 30% with CalB on carrier 350 at 40°C) using this mild lipase-mediated epoxidation method. Enzyme activities and limonene dioxide yields strongly depend on the nature of the selected enzyme carrier, the immobilization method and the reaction temperature.
- Wiemann, Lars O.,Faltl, Christina,Sieber, Volker
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- Magnetic nanoparticles supported manganese(III) tetrapyridylporphyrin catalyst via covalent interaction: A highly efficient and reusable catalyst for the oxidation of hydrocarbons
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In the present work, the highly efficient epoxidation of alkenes and hydroxylation of alkanes catalyzed by tetra(4-N-pyridyl) porphyrinatomanganese(III) acetate, [Mn(TPyP)OAc], supported on silica coated magnetite nanoparticles, SiO2-Fe3O4, are reported. First, the SiO2-Fe3O4 nanoparticles were modified with triethoxysilylpropyl chloride and then [Mn(TPyP)OAc] was attached to the support via covalent linkages. The prepared catalyst was characterized by elemental analysis, FT-IR spectroscopy, diffuse reflectance UV-Vis spectrophotometry and scanning electron microscopy. This new heterogenized catalyst was used for efficient epoxidation of alkenes and hydroxylation of alkanes with NaIO4 at room temperature. This new heterogeneous catalyst is of high reusability in the oxidation reactions, in which the catalyst was reused several times without significant loss of its catalytic activity.
- Saeedi, Mohammad Saleh,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad Reza
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- Efficient and selective epoxidation of alkenes with sodium periodate using supported manganese porphyrins under ultrasonic irradiation
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Epoxides are readily obtained in high yields and good selectivities by ultrasonic irradiation of alkenes and sodium periodate in the presence of catalytic amounts of manganese porphyrins supported on polyvinylpyridine and IRA-900 ion-exchange resin.
- Tangestaninejad, Shahram,Mirkhani, Valiollah
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- Alkene Epoxidation catalysed by Camphor-derived β-Ketophosphonate Complexes of Molybdenum(VI)
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New β-ketophosphonates (L) have been prepared from (R)- or (S)-camphor with various substituents on the phosphorus atom and reacted with to form complexes .These complexes have been used to give highly active catalysts for epoxidation of alkenes by t-BuOOH.Very fast initial rates (ca. 400 catalyst turnovers in the first minute) gave way to much slower rates because the hemi-labile β-ketophosphonate is displaced by a diol ligand.In the presence of molecular sieves, the fast initial stage of the reaction is extended and for styrene, which gives low conversions followed by degradation in the absence of molecular sieves, styrene oxide can be formed with 98percent conversion and 94percent selectivity.It is demonstrated that both the t-BuOOH and the catalyst bind to the molecular sieves, the latter with loss of the β-ketophosphonate ligand.
- Clarke, Russell,Gahagan, Michael,Mackie, Raymond K.,Foster, Douglas F.,Cole-Hamilton, David J.,et al.
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- Viable route and DFT study for the synthesis of optically active limonaketone: A barely available natural feedstock in Cedrus atlantica
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Herein, we report a novel, easy and efficient synthesis pathway of optically active limonaketone, a high added value monoterpene, starting from limonene, natural and low-cost feedstock. The strategy was developed in an excellent three-step total synthesis of limonaketone, potentially important intermediate in limonene ozonolysis and barely available in Cedrus atlantica essential oil (0.1% yield). The first step was the epoxidation of limonene which proceed in 91% yield. The ozonolysis of the prepared limonene oxide leads to the formation of the characteristic ketone function of limonaketone in 92% yield. The last step was performed by a deoxygenation in the presence of Zn and gave limonaketone in quantitative yield. The optically pure limonaketone has been efficiently synthesized from limonene and the overall yield was 84%. A molecular electron density theory (MEDT) analysis was carried out by using density functional theory (DFT) calculations at the M06–2X/6–311G(d,p) (LANL2DZ for Zn) level to understand the observed chemoselectivity in the Zn-deoxygenation reaction as well as its corresponding mechanistic pathway.
- Mekkaoui, Ayoub Abdelkader,Ben El Ayouchia, Hicham,Anane, Hafid,Chahboun, Rachid,El Firdoussi, Larbi,El Houssame, Soufiane
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- Hydrophobic effect of silica functionalized with silylated Ti-salicylaldimine complex on limonene oxidation by aqueous hydrogen peroxide
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This research work describes the effect of hydrophobicity in inducing the diffusion of alkene substrates to the catalytic active sites. The aim of this research is to improve the catalytic activity by tailoring the degree of hydrophobicity of the catalyst. Silica functionalized with solid non-silylated Ti-salicylaldimine complex was prepared at room temperature by mixing imine ligand and Ti(IV) sulphate solution. The amorphous, solid complex formed was further silylated with octadecyltrimethoxysilane (OTMS) to induce hydrophobicity. The composition of the resulting silica functionalized with silylated Ti-salicylaldimine complex was varied with Ti:OTMS molar ratio in the range of 1:1/4 to 1:4 at room temperature. The successful attachment of alkylsilyl groups to silica functionalized with Ti-salicylaldimine complex was proven by the FTIR and 29Si solid state NMR spectra. The FTIR spectra showed increasing peak area for sp 3 C-H stretching mode (ca. 2919 cm-1 and 2850 cm-1) and decreasing peak area for Si-OH band with increasing amount of OTMS. TGA showed less water content with higher amount of alkylsilyl groups in the catalyst. This is in agreement with the lower kinetic rate of water adsorption capacity for the hydrophobic catalysts prepared. It was observed that the hydrophobic, silica functionalized with silylated Ti-salicylaldimine complex exhibited higher substrate conversion and reusability compared to the non-silylated catalyst.
- Yuan, Lai Sin,Chandren, Sheela,Efendi, Jon,Ho, Chin Siong,Nur, Hadi
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- 5-Hydroperoxycarbonylphthalimide: A new reagent for epoxidation
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Peroxycarboxylic acids, widely used for epoxidation in industry and general research, have various drawbacks, such as difficulty of preparation in a pure state, cost and the possibly ring-opening of the product epoxides due to acid-catalysed reactions; a new reagent, 5-hydroperoxycarbonylphthalimide, overcomes these problems.
- James, Alun P.,Johnstone, Robert A.W.,McCarron, Moya,Sankey, J. Phillip,Trenbirth, Brian
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- Studies on olefin epoxidation with t-BuOOH catalysed by dioxomolybdenum(VI) complexes of a novel chiral pyridyl alcoholate ligand
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The chiral dioxomolybdenum(VI) complexes [MoCl{(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}(O)2 (THF)] and [Mo{(1R,2S,5S)-8-trimethylsilyloxy-1-(2-pyridyl)mentholato}2(O) 2] have been prepared in good yields by reaction of the solvent substituted complex [MoCl2O2(THF)2] with one or two equivalents of chiral 2′-pyridyl alcohol. The optically active aminoalcohol was obtained by reaction of 2-pyridyllithium with (-)-(2S,5S)-8-trimethylsilyloxymenthone. The complexes are active catalysts in the homogeneous epoxidation of cyclic and linear olefins, dienes and terpenes by t-BuOOH. They present remarkable activity and excellent product selectivity in cyclooctene epoxidation (cyclooctene oxide was obtained in quantitative yield). In the case of limonene, regioselectivity is high in favour of the epoxidation of the internal cyclic double bond. Ring opening activity was also observed for α-pinene oxide, producing campholenic aldehyde and epoxy campholenic aldehyde.
- Valente,Goncalves,Lopes,Rodriguez-Borges,Pillinger,Romao,Rocha,Garcia-Mera
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- A High Activity Molybdenum containing Epoxidation Catalyst and its Use in Regioselective Epoxidation of Polybutadiene
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MoO2Cl2 is a highly active catalyst for the epoxidation of alkenes by ButOOH; for polybutadiene containing cis-1,4-, trans-1,4-, and 1,2-polymerised units, very high selectivity to the backbone double bonds is observed.
- Gahagan, Michael,Iraqi, Ahmed,Cupertino, Domenico C.,Mackie, Raymond K.,Cole-Hamilton, David J.
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- Efficient epoxidation of olefins by H2O2 catalyzed by iron "helmet" phthalocyanines
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High yields of epoxides were obtained in the oxidation of a large range of olefins using 1.2-2 equiv. of H2O2 in the presence of iron helmet phthalocyanines. The involvement of high-valent iron oxo species was evidenced using cryospray mass spectrometry.
- Skobelev, Igor Y.,Kudrik, Evgeny V.,Zalomaeva, Olga V.,Albrieux, Florian,Afanasiev, Pavel,Kholdeeva, Oxana A.,Sorokin, Alexander B.
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- Heterogeneous catalysis with an organic-inorganic hybrid based on MoO3chains decorated with 2,2′-biimidazole ligands
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The discovery of selective heterogeneous catalytic systems for industrial oxidation processes remains a challenge. Molybdenum oxide-based polymeric hybrid materials have been shown to be oxidation catalysts under mild reaction conditions, although difficulties remain with catalyst recovery/reuse since most perform as homogeneous catalysts or possess low activity. The present study shows that the hybrid material [MoO3(2,2′-biimidazole)]·H2O (1) is a superior catalyst regarding these issues. The structure of1was confirmed (by single crystal and synchrotron X-ray powder diffraction) to comprise one-dimensional chains of corner-sharing {MoO4N2} octahedra. Strong MoO?H-N hydrogen bonds separate adjacent chains to afford parallel channels that are occupied by disordered water molecules. Hybrid1was additionally characterised by FT-IR spectroscopy,1H and13C MAS NMR, scanning electron microscopy and thermogravimetric analysis. The catalytic studies highlighted the versatility of1for oxidation reactions withtert-butylhydroperoxide as oxidant. By complementing with characterisation studies, it was verified that the reaction occurs in the heterogeneous phase, the catalyst has good stability and is recoverableviasimple procedures. The chemical reaction scope covered epoxidation and sulfoxidation, and the substrate scope included biomass-deriveddl-limonene and fatty acid methyl esters to give renewable bio-products, as well as thiophene and thioanisole substrates.
- Amarante, Tatiana R.,Neves, Patrícia,Almeida Paz, Filipe A.,Gomes, Ana C.,Pillinger, Martyn,Valente, Anabela A.,Gon?alves, Isabel S.
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- A polyhedral oligomeric silsesquioxane (POSS)-bridged oxo-molybdenum Schiff base complex with enhanced heterogeneous catalytic activity in epoxidation
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We have generated a new heterogeneous catalyst by bridging an oxo-molybdenum Schiff base on a polyhedral oligomeric silsesquioxane (POSS) via covalent attachment. The resulting POSS-bridged oxo-molybdenum Schiff base complex catalyst was fully characterized by 1H NMR, XRD, FT-IR, SEM, TGA, and contact angle analysis, and its catalytic potential was studied for the epoxidation of alkenes using aqueous tert-butyl hydroperoxide (TBHP) as the oxidant. The catalyst was found to be highly efficient and showed higher catalytic reactivity than the corresponding homogeneous analogues with added benefits of facile recovery and recycling of the heterogeneous catalyst. The POSS-bridged oxo-molybdenum Schiff base complex was successfully reused for four runs without significant loss in activity. The unique three dimensional network catalyst structure and the hydrophobic properties of the POSS units in the catalyst are revealed to be responsible for the catalyst's excellent performance in epoxidation reactions. This journal is the Partner Organisations 2014.
- Leng, Yan,Liu, Jian,Zhang, Chenjun,Jiang, Pingping
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- Anchoring of a terpyridine-based Mo(VI) complex on manganese ferrite as a recoverable catalyst for epoxidation of olefins under solvent-free conditions
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A magnetically separable heterogeneous nanocatalyst was obtained by anchoring a terpyridine-based Mo(VI) complex on modified MnFe2O4 nanoparticles and characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and diffuse reflectance spectroscopies (DRS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis. The catalytic activity of the supported molybdenum based catalyst was evaluated in the selective epoxidation of various olefins (cyclooctene, limonene, 1-dodecane, 1-heptene, styrene, 1-indene, α-pinene, cyclohexene) with tert-butyl hydroperoxide (TBHP) as an oxidant under solvent-free conditions. This nanocatalyst was easily separated by using an external magnetic field and reused consecutively at least five times with no significant loss in selectivity and catalytic activity. The short reaction time, simple preparation, high conversion, good physicochemical stability and magnetic recycling of the catalysts are beneficial.
- Fadaei Sarabi, Mahsa,Bezaatpour, Abolfazl,Mahmoudi, Ali
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- Fine-tuning the local structure and catalytic activity of titanium-amine functionalized silica in oxidation of limonene by aqueous hydrogen peroxide
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Titanium-amine functionalized silica was successfully prepared by a so-called one-pot approach by using 3-aminopropyltrimethoxysilane (APTMS), tetraethoxysilane (TEOS) and titanium(IV) sulfate as precursors. It is demonstrated that the TEOS/APTMS molar ratio in the synthesis of titanium-amine functionalized silica affected the local coordination of titanium and its corresponding positive impact on catalytic activity in oxidation of limonene by aqueous hydrogen peroxide.
- Yuan, Lai Sin,Efendi, Jon,Razali, Nur Syafiqa Hazirah,Nur, Hadi
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- Selective epoxidation of (+)-limonene employing methyltrioxorhenium as catalyst
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This report presents a study of the epoxidation of limonene employing methyltrioxorhenium (MTO) as catalyst. The influence of base ligands, namely t-butylpyridine, 4,4′-dimethyl-2,2′-bipyridine and pyrazole on the catalytic activity was investigated. The choice of the oxidant (H 2O2 in water or H2O2 stabilized by urea) was also examined. The effect of the solvent has been studied in order to determine optimal conditions for the epoxidation of (+)-limonene. The best result was obtained when a molar ratio (+)-limonene:MTO:H2O 2:t-butylpyridine of 100:0.5:10:150 was used at 25 °C in dichloromethane. 1,2-Limonene oxide was formed with 77% yield and 96% selectivity after 1 h with a TOF of ca. 900 h-1.
- Michel, Typhne,Cokoja, Mirza,Sieber, Volker,Kühn, Fritz E.
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- An Efficient Route to Selective Bio-oxidation Catalysts: an Iterative Approach Comprising Modeling, Diversification, and Screening, Based on CYP102A1
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Perillyl alcohol is the terminal hydroxylation product of the cheap and readily available terpene, limonene. It has high potential as an anti-tumor substance, but is of limited availability. In principle, cytochrome P450 monooxygenases, such as the self-sufficient CYP102A1, are promising catalysts for the oxidation of limonene or other inert hydrocarbons. The wild-type enzyme converts (4R)-limonene to four different oxidation products; however, terminal hydroxylation at the allylic C7 is not observed. Here we describe a generic strategy to engineer this widely used enzyme to hydroxylate exclusively the exposed, but chemically less reactive, primary C7 in the presence of other reactive positions. The approach presented here turns CYP102A1 into a highly selective catalyst with a shifted product spectra by successive rounds of modeling, the design of small focused libraries, and screening. In the first round a minimal CYP102A1 mutant library was rationally designed. It contained variants with improved or strongly shifted regio-, stereo- and chemoselectivity, compared to wild-type. From this library the variant with the highest perillyl alcohol ratio was fine-tuned by two additional rounds of molecular modeling, diversification, and screening. In total only 29 variants needed to be screened to identify the triple mutant A264V/A238V/L437F that converts (4R)-limonene to perillyl alcohol with a selectivity of 97%. Focusing mutagenesis on a small number of relevant positions identified by computational approaches is the key for efficient screening for enzyme selectivity. Successive rounds of modeling (MD simulations of enzyme-substrate complexes to identify hotspots for selectivity), diversification (design of minimal library) and screening of a minimal library is shown to be an efficient approach to shift and maximize regioselectivity of CYP102A1, and thus to generate the valuable oxidation product perillyl alcohol from cheap and readily available limonene.
- Seifert, Alexander,Antonovici, Mihaela,Hauer, Bernhard,Pleiss, Juergen
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- Niobium metallocenes deposited onto mesoporous silica via dry impregnation as catalysts for selective epoxidation of alkenes
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A series of niobium catalysts for the selective epoxidation was synthesised by post-synthesis modification of a commercial silica, starting from niobocene dichloride through solventless organometallic precursor dry impregnation (OM-DI) or conventional liquid-phase grafting technique. OM-DI showed to be cheaper, more versatile, less time-consuming and avoided the use of environmentally unfriendly chlorinated solvents. Nb-SiO2 catalysts displayed an excellent performance in the epoxidation of limonene, using aqueous hydrogen peroxide as oxidant. Niobium-silica catalysts were obtained via OM-DI for the first time in this occasion. They showed conversions up to 78% and chemoselectivity to epoxide of 98%. An unexpected regioselectivity to exocyclic epoxide was also observed.
- Gallo, Alessandro,Tiozzo, Cristina,Psaro, Rinaldo,Carniato, Fabio,Guidotti, Matteo
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- Evaluation of antiparasitic activity of mentha crispa essential oil, its major constituent rotundifolone and analogues against trypanosoma brucei
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Considering the pressing need for new drugs to treat sleeping sickness and Nagana disease, Mentha crispa essential oil, its principal constituent rotundifolone, and four related p-menthane-Type monoterpenes (two stereoisomers of limonene epoxide, perillyl alcohol, and perillyl aldehyde) were investigated for their activity against bloodstream forms of Trypanosoma brucei. The general cytotoxicity of the compounds was determined with human myeloid HL-60 cells. The effect of the M. crispa essential oil and the monoterpenes on the growth of parasite and human cells was evaluated in cell cultures with the resazurin viability assay. Of all of the compounds tested, M. crispa essential oil, rotundifolone, and perillyl aldehyde showed the highest trypanocidal activities with 50% growth inhibition (GI50) and minimum inhibitory concentration values of 0.3 μg/ mL and 1 μg/mL, respectively. In contrast, HL-60 cells were considerably less sensitive to the compounds with minimum inhibitory concentration values of 100 μg/mL and GI50 values ranging between 3.4 to 13.8 μg/mL. As a consequence of this, GI50 and minimum inhibitory concentration ratios of cytotoxic to trypanocidal activity (selectivity index) of these three compounds were promising with values of 11-45 and 100, respectively. These results indicate that the p-menthane-Type monoterpenes rotundifolone and perillyl aldehyde are interesting lead candidates for further rational antitrypanosomal drug development.
- De Sousa, Dami?o Pergentino,Lima, Tamires Cardoso,Steverding, Dietmar
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- Cobalt catalyzed oxidation of cyclic alkenes with molecular oxygen: Allylic oxidation versus double bond attack
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Cobalt (II) Schiff's base complex 1 and 2 exhibit a remarkable chemoselectivity during oxidation of cyclic alkenes with molecular oxygen in the presence of 2-methylpropanal. Catalyst 1 encourages the oxidation of double bond to give epoxide as the major product whereas catalyst 2 promotes mainly the allylic oxidation leading to allylic alcohols or enones.
- Madhava Reddy,Punniyamurthy,Iqbal, Javed
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- New poly(organophosphazene) - Supported cobalt or copper (II) catalysts for the oxidation of alkenes
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Polymer-supported heterogeneous catalysts in form of complexes of poly[bis(pyridine-2-oxy)phosphazene] with cobalt(II) or copper(II) acetate were synthesized. The catalysts were prepared by a three-step reaction procedure. First, poly(dichlorophosphazene) was synthesized by thermal polymerization of cyclic trimer of hexachlorocyclotriphosphazene. In the second stage, the poly(dichlorophosphazene) structure was converted into the 2-hydroxypyridine by a nucleophilic substitution reaction. The last stage of the catalyst synthesis was the reaction of poly[bis(pyridine-2-oxy)phosphazene] with cobalt acetate or copper acetate. FTIR, 31P NMR, AAS, BET, SEM, SEM-EDS and TG were employed for characterization of the obtained catalysts. The complexes were applied as heterogeneous catalysts in oxidation of dodecene, indene, limonene in the presence of molecular oxygen in acetonitrile (as solvent) at 60C, using isobutyraldehyde as an oxygen transfer agent. Oxidation reactions of aliphatic and aromatic hydrocarbons let to formation of epoxides or ketones with good yield and high selectivity.
- Blaz,Pielichowski
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p. 345/[711]-355/[721]
(2008)
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- The studies on the limonene oxidation over the microporous TS-1 catalyst
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The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1 catalyst were carried out. The influence of the following parameters was examined: the temperature 0-120 °C, the molar ratio of limonene/H2O2 = 1:2-5:1, methanol concentration 60-95 wt%, TS-1 content 0.25-8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial conditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 °C, the molar ratio of limonene/H2O2 = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very complicated, because during this process also other very useful oxygenated derivatives of limonene can be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be recycled to the oxidation process at least three times.
- Wróblewska, Agnieszka,Makuch, Edyta,Miadlicki, Piotr
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- Solvent-free chromium catalyzed aerobic oxidation of biomass-based alkenes as a route to valuable fragrance compounds
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Chromium containing mesoporous molecular sieves MCM-41 were shown to be an efficient heterogeneous catalyst for the liquid-phase aerobic oxidation of various monoterpenic alkenes under mild solvent-free conditions. The material was prepared through a direct hydrothermal method and characterized by ICP-AES, N2 adsorption-desorption, TEM, XRD, SAXS, and H2-TPR techniques. Characterizations suggest that chromium introduced in MCM-41 is essentially incorporated in the silica framework, with no extraframework chromium oxides being detected. Various oxygenated monoterpenoids important for the flavor and fragrance industry were obtained with high combined selectivities (75-92%) at 30-40% substrate conversions. The oxidation of β-pinene led almost exclusively to allylic mono-oxygenated derivatives, whereas limonene and α-pinene gave both epoxides and allylic oxidation products. The catalyst undergoes no metal leaching and can be easily recovered and re-used. A silica-included chromium catalyst prepared through a conventional sol-gel method showed activity comparable with that of Cr-MCM-41; however, selectivity was much lower.
- Robles-Dutenhefner, Patricia A.,Brand?o, Bruno B.N.S.,De Sousa, Líniker F.,Gusevskaya, Elena V.
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- A simple and efficient oxidation procedure for the synthesis of acid-sensitive epoxides
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A mild and straightforward epoxidation protocol based on sodium perborate as primary oxidant and sodium dehydrocholate as organomediator under homogeneous conditions is described. In particular, geraniol, linalool, 3-carene, and a-pinene are quantitatively converted into the corresponding 6,7-epoxides and transepoxides, respectively. The bile acid salt is recovered from the reaction mixture and may be reused with unchanged efficiency and selectivity. Georg Thieme Verlag Stuttgart.
- Bortolini, Olga,Fantin, Giancarlo,Fogagnolo, Marco
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- New catalysts for the aerobic selective oxidation of hydrocarbons: Mn(III)- and Co(III)-containing molecular sieves for the epoxidation of alkenes
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Co(III) or Mn(III) ions that replace some 4 atom% of Al(III) sites in microporous aluminophosphate number 36 (AlPO-36) function as catalytically active centres for the production from benzaldehyde of acylperoxy radicals: these, in turn, in dry air (30 bar) convert cyclohexene, pinene, limonene and styrene to their corresponding epoxides and diols.
- Raja, Robert,Sankar, Gopinathan,Thomas, John Meurig
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- Phosphotungstates as catalysts for monoterpenes oxidation: Homo- and heterogeneous performance
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Lacunary (PW11), mono-substituted (PW11M) and sandwich type M4(PW9)2 phosphotungstates (M = CoII, FeIII) exhibits high catalytic activity for geraniol and R-(+)-limonene oxidation under mild conditions, using hydrogen peroxide as oxidant and acetonitrile as solvent. The best homogeneous performance was found for the PW11 and for the Co4(PW9)2. Complete conversion of geraniol and R-(+)-limonene was achieved after 1.5 h and 3 h of reaction, respectively, when catalyzed by PW11. The yield of 2,3-epoxygeraniol was 100% in the presence of lacunary PW11 and mono-substituted compounds. PW11 and Co4(PW 9)2 were immobilized on an amine-functionalized SBA-15 (aptesSBA-15) and the composites materials were characterized by FT-IR, FT-Raman, UV-vis/DRS, 31P MAS NMR, elemental analysis and SEM-EDS. Their heterogeneous catalytic activity was investigated for the same substrates and compared with that in homogeneous conditions. The PW11@aptesSBA- 15 and Co4(PW9)2@aptesSBA-15 showed to be active heterogeneous catalysts for geraniol epoxidation with 100% of selectivity for 2,3-epoxide. R-(+)-limonene was also oxidized by PW11@aptesSBA- 15 achieving 90% of conversion after 24 h of reaction. Both composites could be separated after the reaction and reused for at least three cycles without loss of activity. The stability of the heterogeneous catalysts after catalytic reactions was investigated by different techniques of characterization.
- Balula, Salete S.,Santos, Isabel C.M.S.,Cunha-Silva, Luís,Carvalho, Ana P.,Pires, Jo?o,Freire, Cristina,Cavaleiro, José A.S.,De Castro, Baltazar,Cavaleiro, Ana M.V.
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- Olefin epoxidation with tert-BuOOH catalyzed by vanadium polyoxometalate immobilized on ionic liquid-modified MCM-41
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Preparation and characterization of vanadium-containing polyphosphomolybdates supported on ionic liquid-modified MCM-41, MCM-41-Im, are reported. The catalyst, [PVMo@MCM- 41-Im], was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy and also FT-IR, and UV-Vis spectroscopic methods. This heterogeneous catalytic system was applied for efficient epoxidation of various olefins in the presence of tert-BuOOH in 1,2-dichloroethane under reflux. The catalyst can be reused several times without apparent loss of its catalytic performance.
- Hajian, Robabeh,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad Reza
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- Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts
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Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N′-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] (1) and [MoO2Cl2(DEO)] (2). The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55°C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo-1 h-1 could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes 1 and 2 were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity.
- Oliveira, Tania S. M.,Gomes, Ana C.,Lopes, André D.,Louren?o, Jo?o P.,Almeida Paz, Filipe A.,Pillinger, Martyn,Gon?alves, Isabel S.
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- Limonene oxyfunctionalization over Cu-modified silicates employing hydrogen peroxide and t-Butyl hydroperoxide: Reaction pathway analysis
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Limonene oxidation over Cu-nanostructured mesoporous materials was studied. Three solids with different copper content were synthesized employing the template-ion exchange method, and physically-chemically analyzed by a multi-technical characterization. The performance of the molecular sieves as catalysts in the liquid phase oxyfunctionalization of limonene, employing hydrogen peroxide (H2O2) or t-butyl hydroperoxide (TBHP) as oxidants was evaluated. All synthesized Cu-MCM materials were active in the reaction. The obtained results showed that the used oxidant had an important influence on the products distribution under the employed conditions. With H2O2, compounds of high added value such as limonene oxide, carveol and carvone were mainly obtained. Meanwhile, with TBHP, limonene hydroperoxide turned out to be the major product. Finally, a reaction mechanism was proposed for each oxidant.
- Vaschetti, Virginia M.,Cánepa, Analía L.,Barrera, Deicy,Sapag, Karim,Eimer, Griselda A.,Casuscelli, Sandra G.
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- Recyclable solid catalysts for epoxidation of alkenes: Amino- and oniumsilica-immobilized [HPO4{W2O2(μ-O2)2(O2)2}]2- anion
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We designed solid catalysts for liquid-phase epoxidation based on functionalized silica {triple bond, long}Si(CH2)3Q+ [Q: {single bond}NH3, {single bond}NEt3, {single bond}NC5H5, {single bond}PPh3] and [HPO4{W2O2(μ-O2)2(O2)2}]2-. The approach that we adopted allowed us to avoid the use of chlorocarbon solvent and enabled catalyst recycling. By using supports with 4 different linking chains between the anion and silica and different surface lipophilicities, we followed their influence on catalyst activity in the epoxidation of cyclooctene and (R)-limonene by H2O2 in t-BuOH. All solids were active in cyclooctene epoxidation (conversion up to 100%; epoxide selectivity 100%; TOF 2-4 h-1 anion-1). The degree of surface coverage by organic functions was crucial for recycling performance. Catalysts with low densities of organic functions and hydrophilic surfaces were easily deactivated. End-capping improved their stability but decreased their activity. Catalysts with dense coverage of onium groups and the active site in a hydrophobic chloropropyl environment demonstrated high activity and excellent recycling stability. Less promising results were obtained in the epoxidation of (R)-limonene.
- Kovalchuk,Sfihi,Zaitsev,Fraissard
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- Catalytic β-bromohydroxylation of natural terpenes: Useful intermediates for the synthesis of terpenic epoxides
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In a one-step procedure, various β-bromoalcohols were synthesized from natural terpenes in good to excellent yields. Using different catalysts, the reaction was carried out at room temperature, with H2O as nucleophile and N-bromosuccinimide as a bromine source under mild reaction conditions. The synthesized β-bromoalcohols were subsequently converted in situ to the corresponding epoxides in good yields.
- Oubaassine, Saadia,K?ckritz, Angela,Eckelt, Reinhard,Martin, Andreas,Ait Ali, Mustapha,El Firdoussi, Larbi
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- Another example of the instability of a Keggin-type heteropolyanion in the presence of aqueous hydrogen peroxide: From [AsW12O 40]3- to low-nuclearity oxoperoxotungstates - Crystal structure of [(nHex)4N]3-[AsO4{W 2O2(μ-O2)2(O2) 2}2]
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The Keggin dodecatungstoarsenato anion of HNa2[AsW 12O40] is inherently unstable in aqueous hydrogen peroxide and is mainly degraded to [AsO4{W2O2(μ- O2)2(O2)2}2] 3-, [HAsO4{W2O2(μ-O 2)2(O2)2}]2- and [{WO(O2)2(H2O)}2(μ-O)] 2-. These anions were isolated as salts and identified by elemental and spectroscopic analyses. The salt with the formula [(nC6H 13)4]3[AsO4{W2O 2(μ-O2)2(O2)2} 2] was obtained from the reaction of tungstic acid, "H 2WO4" (or HNa2-[AsW12O 40]·nH2O), with aqueous hydrogen peroxide, HNa 2[AsO4]·7H2O and [(nC6H 13)4N]Cl. The structure was refined with R1 = 0.058 and wR2 = 0.067 [monoclinic C2 (no. 5); a = 20.516(6) A, b = 15.923(4) A, c = 14.902(2) A, β = 91.64(1)°, Z = 2], The vibrational spectra (IR and Raman) suggest that the overall structure is maintained in organic solvents. The close relation between the phosphate- and arsenate-based complexes indicates that fluxional behaviour may exist for all these di- and tetranuclear complexes. Fluxionality may play a key role in the transfer of active oxygen (from peroxo groups) to organic substrates via {WO(O2)2} units. It is shown that the heteroligand [XOp]n- (X = As, HAs, MeAs, P, HP, etc.) has a marked effect on the stoichiometric and regioselective epoxidation of (R)-(+)-limonene to 1,2-epoxide at ambient temperature, for a given pH of the aqueous phase. The oxodiperoxo complexes can be used to carry out epoxidation stoichiometrically and regioselectively with (R)-(+)-limonene, but can also be employed in a catalytic process in a two-phase mixture at room temperature. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Piquemal, Jean-Yves,Salles, Laurent,Chottard, Genevieve,Herson, Patrick,Ahcine, Chehrazed,Bregeault, Jean-Marie
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- Oxidation reactions catalyzed by polyoxomolybdate salts
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Ionic compounds containing the polyoxomolybdate anion [Mo6O 19]2- and [(n-C4H9) 4P]+ (tetra-butylphosphonium), [(n-C4H 9)3P(n-C14H29)]+ (tributyl (tetradecyl)phosphonium), [Bmim]+ (1-butyl-3- methylimidazolium) and [Dbmim]+ (1,2-dimethyl-3-butylimidazolium) cations were prepared and characterized, including the determination of three of the solid state structures by singlecrystal X-ray diffraction. These compounds were applied as catalysts for the epoxidation of olefins with urea hydrogen peroxide (UHP) as oxidant in the ionic liquid [Bmim]PF6. Additionally, the oxidation of sulfides to sulfoxides with hydrogen peroxide (H2O2) in several solvents was investigated. The polyoxomolybdate catalysts showed a good performance for epoxidation of olefins as well as for oxidation of sulfides. Furthermore, the catalysts can be recycled several times in oxidation reactions. We present this methodology for the oxidation reaction in a simple, economically, technically, and environmentally benign manner.
- Zhang, Bo,Li, Su,Poethig, Alexander,Cokoja, Mirza,Zang, Shu-Liang,Herrmann, Wolfgang A.,Kuehn, Fritz E.
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- Epoxidation of limonene over low coordination Ti in Ti- SBA-16
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Epoxidation of limonene was studied over Ti-SBA-16 catalysts prepared using two different post grafting techniques. The first one consisted of an in-situ synthesis of a titanium acetylacetone (ACAC) precursor and the other one used directly TiO(ACAC)2. Reaction conditions such as temperature, concentration of TBHP and solvent polarity were examined. The reaction should be carried out at 75?°C in acetonitrile using a TBHP/limonene molar ratio of 11/6. The conversion of limonene reached 80% with a 1,2-limonene oxide selectivity of 79% for both impregnation methods using Ti-SBA-16 with a Ti/Si atomic ratio of 7.3%. Under the same conditions the 3D pore structure of SBA-16 support favors reactants and products mass transfer compared to the 2D pore structure of SBA-15. No differences in catalytic activity were observed as atomic ratio Ti/Si was varied from 5 to 13.4% in Ti-SBA-16. Repeated catalytic tests showed no change in activity over three process cycles.
- Charbonneau, Luc,Kaliaguine, Serge
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- New Mo(II) complexes in MCM-41 and silica: Synthesis and catalysis
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The new complexes [MoI2(CO)3(L1)] (1) and [MoI2(CO)3(L2)] (2) were prepared from reaction of [MoI2(CO)3(NCMe)2] with the ligands 2-(2′-hydroxyphenyl)imidazoline (L1), and 2-(2′- hydroxyphenyl) benzimidazole (L2). These complexes were immobilized in MCM-41 and in silica gel, by grafting (3- chloropropyl)trimethylsilane on the surface of the materials and allowing it to react with [MoI2(-CO) 3(L1)] (1) or [MoI2(CO)3(L 2)] (2). All the molybdenum derivatives were characterized by NMR and FTIR spectroscopies, which showed coordination of L1 and L 2 in neutral form. The structure of the MCM materials was analyzed by powder X-ray diffraction and nitrogen adsorption isotherms. The catalytic activity of the complexes and materials was tested in several substrates (cis-cyclooctene, styrene, 1- octene, R-(+)limonene, geraniol, cis-hex-3-en-1-ol and trans-hex-2-en-1-ol), using tert-butylhydroperoxide (TBHP) as oxidant. Complexes 1 and 2 were in general the more active catalysts and 100% selective towards the epoxide of cis-cyclooctene. Complex 1 immobilized in silica (Si-Pr-1) was the best material, showing higher conversion than 1 in the oxidation of R-(+)limonene, with comparable selectivity towards the ring epoxide.
- Saraiva, Marta S.,Fernandes, Cristina I.,Nunes, Teresa G.,Nunes, Carla D.,Calhorda, Maria José
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- Benzimidazolic complexes of methyltrioxorhenium(VII): Synthesis and application in catalytic olefin epoxidation
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Seven new Lewis base adducts of methyltrioxorhenium(VII) (MTO) with the general formula CH3ReO3·L (L = bidentate benzimidazolic ligands, namely (L = 2-(2-Pyridinyl)-1H-benzimidazole, 5-methyl-2-(2-pyridyl)benzimidazole, 5-Chloro-2-(2-pyridyl)benzimidazole, 2-(2-Pyridyl)-1H-imidazo-[4,5-b]-pyridine, 2-(2-Quinolyl)benzimidazole, 2-(5-methyl-1H-benzimidazol-2-yl)-quinoline, and 2-(5-chloro-1H-benzimidazol-2- yl)-quinoline)) were prepared. All the complexes were characterized by IR, 1H, 13C NMR, MS and elemental analysis as well as tested as catalysts for olefin epoxidation using 35% aqueous hydrogen peroxide as oxidant under mild condition. The influence of different ligand concentrations was also examined. The results show that the complexes are highly selective in olefin epoxidation and good yields can be obtained when excess ligand is applied.
- Li, Su,Zhang, Bo,Kühn, Fritz. E.
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- Synthesis and catalytic properties in olefin epoxidation of octahedral dichloridodioxidomolybdenum(VI) complexes bearing N,N-dialkylamide ligands: Crystal structure of [Mo2o4(μ2-o)CI2(dmf) 4]
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The catalytic performance of the complexes [MoO2Cl 2(L)2] [L = N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), N,N-dimethylpropionamide (dmpa), N,N-diethylformamide (def) and N,N-diphenylformamide (dpf)] was examined in the epoxidation of cis-cyclooctene with ieri-butyl hydroperoxide (tbhp) at 55 °C and in the absence of a cosolvent. The complexes showed high turnover frequencies in the range of 561-577 molmolMo-1h -1r giving the epoxide as the only product in 298 % yield after 6 h. The reaction rates decreased significantly in consecutive runs carried out by recharging the reactors with olefin and oxidant. On the basis of the IR spectroscopic characterisation of the solids recovered at the end of the catalytic reactions, the decrease in activity is attributed to the formation of dioxido(n-oxido)-molybdenum(VI) dimers. Accordingly, the treatment of [Mo0 2Cl2(dmf)2] with an excess amount of tbhp led to the isolation of [Mo204(μ2-0)Cl 2(dmf)4], which was characterised by single-crystal X-ray diffraction and found to exhibit a catalytic performance very similar to that found in the second runs for the mononuclear complexes. The kinetics of the reaction of [Mo02Cl2(dmf)2] with tbhp was further examined by UV/Vis spectroscopy, allowing rate constants and activation parameters to be determined. For the dpf adduct, the effect of different solvents on cyclooctene epoxidation and the epoxidation of other olefins, namely, (R)-(+)-limonene,αpinene and norbornene, were investigated. Wiley-VCH Verlag GmbH & Co. KGaA.
- Gago, Sandra,Neves, Patricia,Monteiro, Bernardo,Pessego, Marcia,Lopes, Andre D.,Valente, Anabela A.,Almeida Paz, Filipe A.,Pillinger, Martyn,Moreira, Jose,Silva, Carlos M.,Goncalves, Isabel S.
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- Immobilizing of oxo-molybdenum complex on cross-linked copolymer and its catalytic activity for epoxidation reactions
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This work describes the immobilization of molybdenum acetylacetonate oxygen (MoO2(acac)2) on cross-linked porous copolymer support via covalent attachment under mild conditions. The obtained solid product DVB-AA-Mo was fully characterized by FT-IR, TG, CHN elemental analysis, nitrogen adsorption/desorption, and SEM, and was tested for the epoxidation of various alkenes with tert-butyl hydroperoxide (TBHP) as the oxidant. DVB-AA-Mo was proved to be a highly efficient catalyst for epoxidation reactions, it could easily be recovered by filtration and reused for five runs without significant loss in activity.
- Fan, Weizheng,Shi, Dongyang,Feng, Bainian
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- Oxygen Atom Transfer Mechanism for Vanadium-Oxo Porphyrin Complexes Mediated Aerobic Olefin Epoxidation
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The development of catalytic aerobic epoxidation by numerous metal complexes in the presence of aldehyde as a sacrificial reductant (Mukaiyama epoxidation) has been reported, however, comprehensive examination of oxygen atom transfer mechanism involving free radical and highly reactive intermediates has yet to be presented. Herein, meso-tetrakis(pentafluorophenyl) porphyrinatooxidovanadium(IV) (VOTPFPP) was prepared and proved to be efficient toward aerobic olefin epoxidation in the presence of isobutyraldehyde. In situ electron paramagnetic resonance spectroscopy (in situ EPR) showed the generation, transfer pathways and ascription of free radicals in the epoxidation. According to the spectral and computational studies, the side-on vanadium-peroxo complexes are considered as the active intermediate species in the reaction process. In the cyclohexene epoxidation catalyzed by VOTPFPP, the kinetic isotope effect value of 1.0 was obtained, indicating that epoxidation occurred via oxygen atom transfer mechanism. The mechanism was further elucidated using isotopically labeled dioxygen experiments and density functional theory (DFT) calculations.
- Han, Qi,Huang, Jia-Ying,Ji, Hong-Bing,Liu, Xiao-Hui,Tao, Lei-Ming,Xue, Can,Yu, Hai-Yang,Zhou, Xian-Tai,Zou, Wen
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supporting information
p. 115 - 122
(2021/12/04)
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- Mn(III)-Porphyrin Immobilized on the Graphene Oxide-Magnetite Nanocomposite as an Efficient Heterogeneous Catalyst for the Epoxidation of Alkenes
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In this research, β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate [MnTPPBr4(OAc)] (MnPor) was anchored onto a magnetite imidazole-modified graphene oxide nanosheet (Fe3O4.GO.Im). The obtained catalyst (Fe3O4.GO.Im@MnPor) was characterized through Fourier transform infrared (FT-IR) and diffuse reflectance UV–Visible spectrophotometry (DR UV–Vis), powder X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric analysis (TGA) and atomic absorption spectroscopy. The characterization was performed to determine the amount of manganese porphyrin loaded on the GO support. The new immobilized catalyst was employed for the efficient epoxidation of different alkenes with urea hydrogen peroxide (UHP) and acetic acid (HOAc) as oxidant activators under mild conditions. Olefins were oxidized efficiently to their corresponding epoxide with 63–100% selectivity in the presence of Fe3O4.GO.Im@MnPor. Moreover, an remarkable turnover frequency (93) was achieved for the oxidation of α-pinene. The graphene oxide-bound Mn-porphyrin was recovered from the reaction mixture by magnetic decantation and reused several times. Graphic Abstract: [Figure not available: see fulltext.]
- Bahrami, Elnaz,Hajian, Robabeh
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- Catalytic efficacy of 2,2′-bipyridine cobalt(II) complex: Hydrothermal synthesis, x-ray structure and aerobic epoxidation of alkenes
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A mononuclear cobalt(II) complex, [Co(bpy)2(NO3)](NO3)·3H2O (1) (bpy = 2,2′-bipyridine) has been synthesized hydrothermally and the crystal structure was characterized by X-ray crystallography. Complex 1 is capable of activating aerobic oxygen at atmospheric pressure. [Co(bpy)2(NO3)](NO3)·3H2O (1) was used as an active catalyst for the aerobic epoxidaion of various alkenes with isobutyraldehyde as co-reductant in acetonitrile medium. Complex 1 catalyzes the epoxidaion reaction efficiently, which reflected in high yield of products with desired selectivity.
- Bera, Rajesh
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- Rational Construction of an Artificial Binuclear Copper Monooxygenase in a Metal-Organic Framework
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Artificial enzymatic systems are extensively studied to mimic the structures and functions of their natural counterparts. However, there remains a significant gap between structural modeling and catalytic activity in these artificial systems. Herein we report a novel strategy for the construction of an artificial binuclear copper monooxygenase starting from a Ti metal-organic framework (MOF). The deprotonation of the hydroxide groups on the secondary building units (SBUs) of MIL-125(Ti) (MIL = Matériaux de l'Institut Lavoisier) allows for the metalation of the SBUs with closely spaced CuI pairs, which are oxidized by molecular O2 to afford the CuII2(μ2-OH)2 cofactor in the MOF-based artificial binuclear monooxygenase Ti8-Cu2. An artificial mononuclear Cu monooxygenase Ti8-Cu1 was also prepared for comparison. The MOF-based monooxygenases were characterized by a combination of thermogravimetric analysis, inductively coupled plasma-mass spectrometry, X-ray absorption spectroscopy, Fourier-transform infrared spectroscopy, and UV-vis spectroscopy. In the presence of coreductants, Ti8-Cu2 exhibited outstanding catalytic activity toward a wide range of monooxygenation processes, including epoxidation, hydroxylation, Baeyer-Villiger oxidation, and sulfoxidation, with turnover numbers of up to 3450. Ti8-Cu2 showed a turnover frequency at least 17 times higher than that of Ti8-Cu1. Density functional theory calculations revealed O2 activation as the rate-limiting step in the monooxygenation processes. Computational studies further showed that the Cu2 sites in Ti8-Cu2 cooperatively stabilized the Cu-O2 adduct for O-O bond cleavage with 6.6 kcal/mol smaller free energy increase than that of the mononuclear Cu sites in Ti8-Cu1, accounting for the significantly higher catalytic activity of Ti8-Cu2 over Ti8-Cu1.
- Feng, Xuanyu,Song, Yang,Chen, Justin S.,Xu, Ziwan,Dunn, Soren J.,Lin, Wenbin
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supporting information
p. 1107 - 1118
(2021/01/25)
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- New heptacoordinate tungsten(II) complexes with α-diimine ligands in the catalytic oxidation of multifunctional olefins
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New tungsten(II) and molybdenum(II) heptacoordinate complexes [MX2(CO)3(LY)] (MXLy: M = W, Mo; X = Br, I; LY = C5H4NCY = N(CH2)2CH3 with Y = H (L1), Me (L2), Ph (L3)) were synthesized and characterized by spectroscopic techniques and elemental analysis. The two tungsten complexes WXL1 (X = Br, I) were also structurally characterized by single crystal X-ray diffraction. The metal coordination environment is in both a distorted capped octahedron. The complexes with L1 and L2 ligands were grafted in MCM-41, after functionalization of the ligands with a Si(OEt)3 group. The new materials were characterized by elemental analysis, N2 adsorption isotherms, 29Si MAS and 13C MAS NMR. The tungsten(II) complexes and materials were the first examples of this type reported. All complexes and materials were tested as homogeneous and heterogeneous catalysts in the oxidation of multifunctional olefins (cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, geraniol, S-limonene, and 1-octene), with tert-butyl hydroperoxide (TBHP) as oxidant. The molybdenum(II) catalyst precursors are in general very active, reaching 99% conversion and 100% selectivity in the epoxidation of trans-hex-3-en-1-ol. Their performance is comparable with that of the [Mo(η3-C3H5)X(CO)2(LY)] complexes, but it increases with immobilization. On the other hand, most of the W(II) complexes display an activity similar or inferior to that of the Mo(II) analogues and it decreases after they are supported in MCM-41. DFT calculations show that tungsten complexes and iodide ligands are more easily oxidized from M(II) to M(VI) than molybdenum ones, while the energies of relevant species in the catalytic cycle are very similar for all complexes, making the theoretical rationalization of experimental catalytic data difficult.
- Vasconcellos-Dias, Maria,Nunes, Carla D.,Félix, Vítor,Brand?o, Paula,Calhorda, Maria José
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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- Kinetic investigation of aerobic epoxidation of limonene over cobalt substituted mesoporous SBA-16
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Incorporation of low coordination Co2+within the structure of mesoporous silica SBA-16 has been accomplished through a facile and green “pH adjusting” method. The resulting materials were used as heterogeneous catalysts for aerobic Mukaiyama epoxidation of limonene in the presence of isobutyraldehyde, under very mild conditions. The structural integrity during the pH adjustment procedure at various loadings and states of cobalt ions within the mesoporous structure were determined using characterization techniques including nitrogen physisorption, X-ray fluorescence, diffuse reflectance UV-vis, scanning electron microscopy, temperature-programmed reduction, X-ray photoelectron spectroscopy and powder X-ray diffraction. These catalysts showed quite high reactivity for the epoxidation of limonene with high epoxide yields under optimized oxygen pressure. In this work, a thorough kinetic analysis of aerobic epoxidation of limonene was investigated to allow proposing a reaction scheme. A new mechanism, in which a surface reaction between a Co3+OO?peroxo intermediate and limonene was found to be involved in the formation of the epoxidized limonene. The kinetics developed from the proposed mechanism was accurately fitted with extensive experimental initial reaction rate data. The activation energy for limonene mono epoxide formation was determined to be 22 kJ mol?1
- Madadi, Sara,Bergeron, Jean-Yves,Kaliaguine, Serge
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p. 594 - 611
(2021/02/09)
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- A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles
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A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.
- Rossi-Fernández, Lucía,Dorn, Viviana,Radivoy, Gabriel
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supporting information
p. 519 - 526
(2021/03/31)
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- Lipase catalysed oxidations in a sugar-derived natural deep eutectic solvent
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Chemoenzymatic oxidations involving the CAL-B/H2O2 system was developed in a sugar derived Natural Deep Eutectic Solvent (NaDES) composed by a mixture of glucose, fructose and sucrose. Good to excellent conversions of substrates like cyclooctene, limonene, oleic acid and stilbene to their corresponding epoxides, cyclohexanone to its corresponding lactone and 2-phenylacetophenone to its corresponding ester, demonstrate the viability of the sugar NaDES as a reaction medium for epoxidation and Baeyer-Villiger oxidation.
- Vagnoni, Martina,Samorì, Chiara,Pirini, Daniele,Vasquez De Paz, Maria Katrina,Gidey, Dawit Gebremichael,Galletti, Paola
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- A silicododecamolybdate/pyridinium-tetrazole hybrid molecular salt as a catalyst for the epoxidation of bio-derived olefins
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The hybrid polyoxometalate (POM) salt (Hptz)4[SiMo12O40]?nH2O (1) (ptz = 5-(2-pyridyl)tetrazole) has been prepared, characterized by X-ray crystallography, and examined as a catalyst for the epoxidation of cis-cyclooctene (Cy) and bio-derived olefins, namely dl-limonene (Lim; a naturally occurring monoterpene found in the rinds of citrus fruits), methyl oleate and methyl linoleate (fatty acid methyl esters (FAMEs) obtained by transesterification of vegetable oils). The crystal structure of 1 consists of α-Keggin-type heteropolyanions, [SiMo12O40]4-, surrounded by space-filling and charge-balancing 2-(tetrazol-5-yl)pyridinium (Hptz+) cations, as well as by a large number of water molecules of crystallization (n = 9). The water molecules mediate an extensive three-dimensional (3D) hydrogen-bonding network involving the inorganic anions and organic cations. For the epoxidation of the model substrate Cy in a nonaqueous system (tert-butylhydroperoxide as oxidant), the catalytic performance of 1 (100% epoxide yield at 24 h, 70 °C) was superior to that of the tetrabutylammonium salt (Bu4N)4[SiMo12O40] (2) (63% epoxide yield at 24 h), illustrating the role of the counterion Hptz+ in enhancing catalytic activity. The hybrid salt 1 was effective for the epoxidation of Lim (69%/85% conversion at 6 h/24 h) and the FAMEs (87–88%/100% conversion at 6 h/24 h), leading to useful bio-based products (epoxides, diepoxides and diol products).
- Nunes, Martinique S.,Neves, Patrícia,Gomes, Ana C.,Cunha-Silva, Luís,Lopes, André D.,Valente, Anabela A.,Pillinger, Martyn,Gon?alves, Isabel S.
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- A sustainable approach towards solventless organic oxidations catalyzed by polymer immobilized Nb(V)-peroxido compounds with H2O2 as oxidant
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New heterogeneous catalysts comprising of peroxidoniobium(V) complexes immobilized on amino acid grafted cross-linked poly(styrene-divinylbenzene) resin has been developed. Results of FTIR, Raman, NMR, XPS, XRD, EDX, SEM, BET, TGA, and elemental analysis confirmed the successful anchoring of triperoxidoniobium(V), [Nb(O2)3]? species to the host polymer via the pendant amino acid groups. The supported catalysts exhibited excellent performance in epoxidation of styrene and a range of cyclic and terpenic compounds under environmentally acceptable solvent-free condition, with aqueous H2O2 as oxidant. The catalytic protocols provided excellent conversion to the desired epoxide (up to 100%) with selectivity > 99%, TON as high as 1000, and high H2O2 utilization efficiency (92–97%). Moreover, the catalysts efficiently facilitated chemoselective solvent-free oxidation of a variety of thioethers to sulfones at room temperature. Simple operational strategy, easy recyclability for multiple reaction cycles with the consistent activity-selectivity profile are the additional significant attributes of the developed catalytic processes.
- Ahmed, Kabirun,Gogoi, Sandhya Rani,Islam, Nashreen S.,Saikia, Gangutri,Sultana, Sazida Yasmin,Talukdar, Hiya
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- Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions
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The new cis-dioxomolybdenum (VI) complexes [MoO2(L2)(H2O)] (2) and [MoO2(L3)(H2O)] (3) containing the tridentate hydrazone-based ligands (H2L2 = N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)-4-methylbenzohydrazide and H2L3 = N'-(2-hydroxybenzylidene)-2-(hydroxyimino)propanehydrazide) have been synthesized and characterized via IR, 1H and 13C NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction analysis. The catalytic activities of complexes 2 and 3, and the analogous known complex [MoO2(L1)(H2O)] (1) (H2L1 = N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide) have been evaluated for various oxidation reactions, viz. oxygen atom transfer from dimethyl sulfoxide to triphenylphosphine, sulfoxidation of methyl-p-tolylsulfide or epoxidation of different alkenes using tert-butyl hydroperoxide as terminal oxidant. The catalytic activities were found to be comparable for all three complexes, but complexes 1 and 3 showed better catalytic performances than complex 2, which contains a more sterically demanding ligand than the other two complexes.
- Hossain, Md Kamal,Plutenko, Maxym O.,Schachner, J?rg A.,Haukka, Matti,M?sch-Zanetti, Nadia C.,Fritsky, Igor O.,Nordlander, Ebbe
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- Easy Epoxidation of Monoterpenes from Common Starting Materials
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Epoxidation of monoterpenes, α-pinene, β-pinene, limonene, α-terpinene, and (R)-carvone was carried out by the in situ production of a peroxyacid rather than direct addition of such an expensive and difficult to handle chemical. Previous reports showed use of metal catalysts with high yields, while methodologies without catalysts at high temperature showed yields lower than 30%. The authors report a methodology that produces peroxyacetic acid in situ yielding up to 75% pure epoxide at room temperature avoiding the use of catalysts. The products were analyzed by gas chromatography mass spectrometry (GC-MS), and structures were characterized by 1H and 13C nuclear magnetic resonance (NMR).
- Benitez, Ricardo B.,Bermudez, John H.,Franco, Jaime M.,Rojas, Giovanni
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p. 1086 - 1092
(2020/10/14)
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- Homogeneous catalytic oxidation of alkenes employing mononuclear vanadium complex with hydrogen peroxide
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Abstract: Homogeneous liquid-phase oxidation of alkenes (allylbenzene, cis-cyclooctene, 4-chlorostyrene, styrene, 2-norbornene, 1-methyl cyclohexene, indene, lemonine, and 1-hexene) were catalyzed by using vanadium complex [VO(hyap)(acac)2] in existence of H2O2. The complex [VO(hyap)(acac)2] was formed as a crystal by the reaction of [VO(acac)2] and 2-hydroxyacetophenone (hyap) in the presence of methanol by refluxing the reaction mixture. Various analytical and spectroscopic techniques, namely FTIR, ESI–MS, UV–Vis, single-crystal XRD, and EPR, were used to analyze and optimize the structure of the complexes. Graphic abstract: [Figure not available: see fulltext.].
- Maurya, Abhishek
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p. 3261 - 3269
(2020/07/14)
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- Chiral amino and imino-alcohols based on (R)-limonene
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Derivatives of the natural occurring and inexpensive terpene (R)-limonene were synthetized and completely characterized. Starting from internal olefin epoxidation, followed by epoxide opening with sodium azide and azide reduction with LiAlH4, two chiral amino-alcohols were obtained. The amino-alcohols were reacted with three different aldehydes, generating six new imino-alcohols, two of them yielding crystals suitable for X-ray diffraction characterization. The reduction of four of these compounds with LiAlH4 led to new amino-alcohols. All derivatives were obtained with good overall yields through simple reaction protocols.
- Fuscaldo, Rodrigo S.,Boeira, Eduam O.,Stieler, Rafael,Lüdtke, Diogo S.,Gregório, José R.
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p. 438 - 446
(2020/04/27)
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- Selective Allylic Oxidation of Terpenic Olefins Using Co-Ag Supported on SiO2 as a Novel, Efficient, and Recyclable Catalyst
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Co-Ag supported on the SiO2 catalyst was synthesized by the sol-gel method and characterized using XRD, FT-IR, TG-DTG, BET, CV, and SEM/EDX analysis. The catalytic performance of the resulting catalyst was examined by the oxidation of mono and sesquiterpenic olefins using hydrogen peroxide and tert-butyl peroxide as oxidant agents. Various parameters such as catalyst amount, temperature, and solvents have been studied. The Co-Ag supported on the SiO2 catalyst showed a high activity, selectivity, and recyclability for the selected oxidation reaction.
- Aberkouks, Abderrazak,Mekkaoui, Ayoub Abdelkader,Ait Ali, Mustapha,El Firdoussi, Larbi,El Houssame, Soufiane
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- Synthesis of dipyroromethanes in water and investigation of electronic and steric effects in efficiency of olefin epoxidation by sodium periodate catalyzed by manganese tetraaryl and trans disubstituted porphyrin complexes
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Condensation of pyrrole with various aldehydes in the presence of BF3?etherate as an acid catalyst in water provides good yield of some dipyrromethanes. Prolongation of the reaction time with aldehydes substituted by electron-donating (mesityl) or electron-withdrawing (2,6-dichlorophenyl) groups on the ortho positions of the phenyl did not lead to decomposition or scrambling. Manganese trans disubstituted porphyrin complexes which derive from various dipyrromethanes and manganese tetraaryl porphyrin complexes including various substituents with different steric and electronic properties show good catalytic activity in epoxidation of alkenes by NaIO4 in the presence of imidazole (ImH). The study of steric and electronic effects of the catalysts on the epoxidation of olefins shows that Mn-porphyrin complexes with more bulky and electron-releasing groups on meso phenyls could increase the epoxidation yield of most alkenes.
- Bagherzadeh, Mojtaba,Jonaghani, Mohammad Adineh,Amini, Mojtaba,Mortazavi-Manesh, Anahita
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p. 671 - 678
(2019/04/26)
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- Catalytic epoxidation using dioxidomolybdenum(VI) complexes with tridentate aminoalcohol phenol ligands
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Reaction of the tridentate aminoalcohol phenol ligands 2,4-di-tert-butyl-6-(((2 hydroxyethyl)(methyl)amino)methyl)phenol (H2L1) and 2,4-di-tert-butyl-6-(((1-hydroxybutan-2-yl)amino)methyl)phenol (H2L2) with [MoO2(acac)2] in methanol solutions resulted in the formation of [MoO2(L1)(MeOH)] (1) and [MoO2(L2)(MeOH)] (3), respectively. In contrast, the analogous reactions in acetonitrile afforded the dinuclear complexes [Mo2O2(μ-O)2(L1)2] (2) and [Mo2O2(μ-O)2(L2)2] (4). The corresponding reactions with the potentially tetradentate ligand 3-((3,5-di-tert-butyl-2-hydroxybenzyl)(methyl)amino)propane-1,2-diol (H3L3) led to the formation of the mononuclear complex [MoO2(L3)(MeOH)] (5) in methanol while in acetonitrile solution a trinuclear structure [Mo3O3(μ-O)3(L3)3] (6) was obtained. In both cases, the ligand moiety L3 coordinated in a tridentate fashion. The catalytic activities of complexes 1–6 in epoxidation of five different olefins, S1-5, with tert-butyl hydroperoxide and hydrogen peroxide were studied. The catalytic activities were found to be moderate to good for the reaction of substrate cis-cyclooctene S1, while all complexes were less active in the epoxidation of the more challenging substrates S2-5. The molecular structures of 1, 2, 4 and 6 were determined by single crystal X-ray diffraction analyses.
- Hossain, Md. Kamal,Schachner, J?rg A.,Haukka, Matti,M?sch-Zanetti, Nadia C.,Nordlander, Ebbe,Lehtonen, Ari
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- High surface area, nanostructured boehmite and alumina catalysts: Synthesis and application in the sustainable epoxidation of alkenes
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We report a new, straightforward and inexpensive sol-gel route to prepare boehmite nanorods [γ-AlO(OH)-NR] with an average length of 23 nm ± 3 nm, an average diameter of 2 nm ± 0.3 nm and a high specific surface area of 448 m2/g, as evidenced by TEM and N2-physisorption, respectively. The boehmite was converted to γ-alumina with preserved nanorod morphology (γ-Al2O3-NR) and high surface area upon calcination either at 400 or 600 °C. These nanostructured materials are active and selective heterogeneous catalysts for the epoxidation of alkenes with the environmentally friendly H2O2. The best catalyst, γ-Al2O3-NR-400, showed to be versatile in the scope of alkenes that could be converted selectively to their epoxide and displayed enhanced reusability compared to previously reported alumina catalysts. Furthermore, the catalytic performance of the material was enhanced by optimising the reaction conditions such as the solvent and the type of hydrogen peroxide source. Under the optimised reaction conditions, the γ-Al2O3-NR-400 catalyst displayed 58% cyclooctene oxide yield after 4 h of reaction at 80 °C with full selectivity towards the epoxide product. The correlation between the catalytic activity of these materials and their physicochemical properties such as surface area, hydrophilicity and number and type of acid sites was critically discussed based on a detailed characterisation study.
- Lueangchaichaweng, Warunee,Singh, Bhawan,Mandelli, Dalmo,Carvalho, Wagner A.,Fiorilli, Sonia,Pescarmona, Paolo P.
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p. 180 - 187
(2019/01/04)
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- Preparation method of 1S,4R-1-methyl-4-(1-methylvinyl)-2-cyclohexene-1-ol
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The invention relates to a novel synthesis route of 1S,4R-1-methyl-4-(1-methylvinyl)-2-cyclohexene-1-ol. According to the preparation method, limonene is taken as the raw material, 1S,4R-1-methyl-4-(1-methylvinyl)-2-cyclohexene-1-ol is synthesized after four steps: epoxidation reactions, addition reactions, oxidation reactions, and elimination reactions, and the yield is high. The provided 1S,4R-1-methyl-4-(1-methylvinyl)-2-cyclohexene-1-ol preparation method has the advantages of high yield, high chiral purity product, low cost, environmental friendliness, and easy operation, and is suitablefor industrialization.
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Paragraph 0028; 0029
(2019/08/30)
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- Room-Temperature Chemoselective Reductive Alkylation of Amines Catalyzed by a Well-Defined Iron(II) Complex Using Hydrogen
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A transition-metal frustrated Lewis pair approach has been envisaged to enhance the catalytic activity of tricarbonyl phosphine-free iron complexes in reduction of amines. A new cyclopentadienyl iron(II) tricarbonyl complex has been isolated, fully characterized, and applied in hydrogenation. This phosphine-free iron complex is the first Earth-abundant metal complex that is able to catalyze chemoselective reductive alkylation of various functionalized amines with functionalized aldehydes. Such selectivity and functionality tolerance (alkenes, esters, ketones, acetals, unprotected hydroxyl groups, and phosphines) have been demonstrated also for the first time at room temperature with an Earth-abundant metal complex. This alkylation reaction was also performed without any preliminary condensation and generated only water as a byproduct. The resulting amines provided rapid access to potential building blocks, metal ligands, or drugs. Density functional theory calculations highlighted first that the formation of the 16 electron species, via the activation of the tricarbonyl complex Fe3, was facilitated and, second, that the hydrogen cleavage did not follow the same pathway as bond breaking, usually described with the known cyclopentadienone iron tricarbonyl complexes (Fe1 and Fe4). These calculations highlighted that the new complex Fe3 does not behave as a bifunctional catalyst, in contrast to its former congeners.
- Lator, Alexis,Gaillard, Quentin Gaignard,Mérel, Delphine S.,Lohier, Jean-Fran?ois,Gaillard, Sylvain,Poater, Albert,Renaud, Jean-Luc
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p. 6813 - 6829
(2019/06/07)
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- Exploring the substrate specificity of Cytochrome P450cin
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Cytochromes P450 are enzymes that catalyse the oxidation of a wide variety of compounds that range from small volatile compounds, such as monoterpenes to larger compounds like steroids. These enzymes can be modified to selectively oxidise substrates of interest, thereby making them attractive for applications in the biotechnology industry. In this study, we screened a small library of terpenes and terpenoid compounds against P450cin and two P450cin mutants, N242A and N242T, that have previously been shown to affect selectivity. Initial screening indicated that P450cin could catalyse the oxidation of most of the monoterpenes tested; however, sesquiterpenes were not substrates for this enzyme or the N242A mutant. Additionally, both P450cin mutants were found to be able to oxidise other bicyclic monoterpenes. For example, the oxidation of (R)- and (S)-camphor by N242T favoured the production of 5-endo-hydroxycamphor (65–77% of the total products, dependent on the enantiomer), which was similar to that previously observed for (R)-camphor with N242A (73%). Selectivity was also observed for both (R)- and (S)-limonene where N242A predominantly produced the cis-limonene 1,2-epoxide (80% of the products following (R)-limonene oxidation) as compared to P450cin (23% of the total products with (R)-limonene). Of the three enzymes screened, only P450cin was observed to catalyse the oxidation of the aromatic terpene p-cymene. All six possible hydroxylation products were generated from an in vivo expression system catalysing the oxidation of p-cymene and were assigned based on 1H NMR and GC-MS fragmentation patterns. Overall, these results have provided the foundation for pursuing new P450cin mutants that can selectively oxidise various monoterpenes for biocatalytic applications.
- Stok, Jeanette E.,Giang, Peter D.,Wong, Siew Hoon,De Voss, James J.
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- A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons
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Mixed-metal metal organic frameworks have received considerable attention in recent years and it has been shown that the activity of the parent metal organic framework (MOF) is often enhanced upon doping with external metal ions within the framework. In this context, Cu2+ ions with different loadings were incorporated within the ZIF-8 framework to obtain a series of Cu-doped ZIF-8 materials and their activity was examined in the aerobic oxidation of hydrocarbons. The as-synthesized Cu-doped solids were characterized by powder X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), Fourier Transform infrared (FT-IR), electron paramagnetic resonance (EPR) and inductively coupled plasma (ICP) analysis. The experimental results revealed that the activity of Cu-doped ZIF-8 is much higher than that of the parent ZIF-8 in all the tested substrates at 120 °C. Furthermore, the activity of the Cu-doped ZIF-8 with the highest Cu loading was eight fold higher than that of the parent ZIF-8 in the aerobic oxidation of cyclooctane (1) at 120 °C with more than 80% selectivity to the corresponding cyclooctanol/cyclooctanone (ol/one) mixture. Cu-doped ZIF-8 was reused two times with no significant drop in its activity under identical conditions. Furthermore, comparison of the two times reused solid with that of the fresh solid by powder XRD and SEM analysis revealed identical structural integrity and morphology, respectively during the oxidation reactions.
- Nagarjun, Nagarathinam,Dhakshinamoorthy, Amarajothi
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p. 18702 - 18712
(2019/12/09)
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- 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content oxidant in various oxidative reactions
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Several oxidative approaches namely thiocyanation of aromatic compounds, epoxidation of alkenes, amidation of aromatic aldehydes, epoxidation of α β-unsaturated ketones, oxidation of sulfides to sulfoxides and sulfones, bayer-villeger reaction, bromination and iodation of aniline and phenol derivatives oxidative esterification, oxidation of pyridines and oxidation of secondary, allylic and benzyllic alcohols were carried out using 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane as the potential solid oxidant which can be stored for several months without any loss in its activity. All of the procedures were accomplished via mild reaction conditions and the products were afforded in high yields and short reaction times.
- Khosravi, Kaveh,Naserifar, Shirin
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supporting information
p. 6584 - 6592
(2018/10/05)
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- Molybdenum(0) tricarbonyl and tetracarbonyl complexes with a cationic pyrazolylpyridine ligand: Synthesis, crystal structures and catalytic performance in olefin epoxidation
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The synthesis of molybdenum(0) tricarbonyl and tetracarbonyl complexes of the form [Mo(CO)3(ptapzpy)Br] (1) and cis-[Mo(CO)4(ptapzpy)]Br (2) is reported, where ptapzpy = 2-(1-propyltrimethylammonium-3-pyrazolyl)pyridine. Preparation of these derivatives was accomplished either through thermal replacement of CO in Mo(CO)6 (for 1) or substitution under milder conditions of piperidine ligands in the precursor cis-[Mo(CO)4(pip)2] (for 2). The crystal structures of the ligand [ptapzpy]Br and complexes 1 and 2 were determined. Thermal treatment of 2 at 125-150 °C leads to mono decarbonylation and formation of 1. On the other hand, oxidative decarbonylation of 1 and 2 by reaction with tert-butylhydroperoxide (TBHP, 10 equiv.) gives a molybdenum oxide hybrid material formulated as [Mo3O9([ptapzpy]Br)2]·nH2O (3), which was characterised by FT-IR and Raman spectroscopy, thermogravimetric analysis, and 13C{1H} CP MAS NMR spectroscopy. Compounds 1-3 were effective (pre)catalysts for the epoxidation of cis-cyclooctene at 55 °C with aqueous H2O2 or TBHP (slightly better results were obtained with the former). The characterisation of the Mo-containing solids isolated after the catalytic reaction showed that poorly soluble β-octamolybdate salts, (L)x[Mo8O26], were formed from 1-3 with TBHP and from 1 with H2O2, while soluble oxoperoxo species were formed from 3 with H2O2. These findings helped to explain the different catalytic performances obtained.
- Nogueira, Lucie S.,Neves, Patrícia,Gomes, Ana C.,Lavrador, Pedro,Cunha-Silva, Luís,Valente, Anabela A.,Gon?alves, Isabel S.,Pillinger, Martyn
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p. 16294 - 16302
(2018/05/22)
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- Cu(II)/Cu(II)-Mg(II) containing pyridine-2,5-dicarboxylate frameworks: Synthesis, structural diversity, inter-conversion and heterogeneous catalytic epoxidation
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Ligand concentration dependent structural diversity and inter-conversion of hydrothermally synthesized metal carboxylate compounds, {[Mg(H2O)6][Cu(pdc)2]·2H2O}n (1), {[CuMg(pdc)2(H2O)4]·2H2O}n (2), {2(Him)·[Cu(pdc)2]}n (3), and {[Cu(pdc)(im)2]·2H2O}n (4) (H2Pdc = pyridine-2,5-dicarboxylic acid and im = imidazole), have been thoroughly investigated. Formation of compounds 1–4 depends on the concentration of imidazole. Structure of all four compounds has been verified by single crystal X-ray diffraction and other physicochemical studies. Compound 3 catalyzes olefin epoxidation reaction in heterogeneous condition.
- Saha, Debraj,Gayen, Saikat,Koner, Subratanath
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- Immobilization of a Molybdenum Complex on Bipyridine-Based Periodic Mesoporous Organosilica and Its Catalytic Activity for Epoxidation of Olefins
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The dichlorodioxomolybdenum(VI) complex (MoO2Cl2) is an efficient and low-cost homogeneous catalyst for a variety of organic reactions, but its activity usually decreases after immobilization on a solid support. This report describes the synthesis of heterogeneous Mo complex catalysts using a bipyridine-periodic mesoporous organosilica (BPy-PMO) as a solid chelating ligand and MoO2Cl2 as a precursor, and their catalysis in the epoxidation of olefins with tert-butyl hydroperoxide (TBHP). The MoO2Cl(OH) complex could be immobilized on trimethylsilylated BPy-PMO (BPy-PMO-TMS), which was confirmed by Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray absorption fine-structure analysis. The Mo complex immobilized on BPy-PMO-TMS exhibited greater catalytic activity for the epoxidation of cis-cyclooctene compared with conventional heterogeneous Mo complex catalysts using mesoporous silica, polystyrene, and naked BPy-PMO as supports. A large amount (up to 0.72 mmol g-1) of the Mo complex could be loaded on BPy-PMO-TMS, which resulted in 37% of the exposed bipyridine ligands on the surface forming Mo complexes. The turnover frequency relative to Mo was nearly constant, even with a high density of Mo complex on the pore surface. The Mo-BPy-PMO-TMS catalyst exhibited a solvent effect on the catalysis, and the presence of water in the reaction medium was detrimental for the catalysis. Under anhydrous conditions, Mo-BPy-PMO-TMS showed good catalytic activity for at least three reuse cycles in the epoxidation of cis-cyclooctene. A variety of olefins including aliphatic and aromatic olefins were successfully oxidized by Mo-BPy-PMO-TMS to give the desired epoxides in high yield.
- Ishikawa, Satoshi,Maegawa, Yoshifumi,Waki, Minoru,Inagaki, Shinji
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p. 4160 - 4169
(2018/05/22)
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- New perspective to catalytic epoxidation of olefins by Keplerate containing Keggin polyoxometalates
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Different Keggin encapsulated in Keplerate polyoxometalates (Mo72Fe30, PMo12 ? Mo72Fe30, SiMo12 ? Mo72Fe30 and BW12 ? Mo72Fe30) have been synthesized and their catalytic efficiency in the epoxidation of olefins with hydrogen peroxide investigated. Results were confirmed that Keggin encapsulated in Keplerates could show higher catalytic activity than parent ones. These POM catalysts lead to heterogeneous epoxidation of alkenes by hydrogen peroxide with green features of convenient recovery, steady reuse, high conversion and selectivity, and simple preparation.
- Taghiyar, Hamid,Yadollahi, Bahram
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supporting information
p. 98 - 104
(2018/10/05)
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- High-yield synthesis and catalytic response of chainlike hybrid materials of the [(MoO3): M(2,2′-bipyridine)n] family
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The one-dimensional organic-inorganic hybrid material [MoO3(2,2′-bipy)] (1) (2,2′-bipy = 2,2′-bipyridine) has been used as a starting material to prepare the bipy-deficient phases [Mo2O6(2,2′-bipy)] (2) and [Mo3O9(2,2′-bipy)2] (3) in excellent yields. The hybrid 2 was obtained by a solid-state thermal treatment of 1 (300 °C, 10 min) while 3 was obtained by a hydrothermal treatment of 1 (160 °C, 6 d). A study was performed to compare the catalytic properties of 1-3 in the epoxidation of cis-cyclooctene at 55 °C with tert-butylhydroperoxide (TBHP) or aqueous H2O2 as oxidant. In all cases Cy was converted to cyclooctene oxide (CyO) with 100% selectivity, and Cy conversions increased in the order 1 2O2 (cosolvent CH3CN). The catalytic reactions occurred in homogeneous phase with active species formed in situ from 1-3. All three hybrids react with aqueous H2O2 to give the catalytically active oxodiperoxo complex [MoO(O2)2(2,2′-bipy)]. The 2:1 hybrid 2 was further examined for the epoxidation of other cyclic and linear non-functionalised olefins with TBHP, namely cyclododecene, 1-octene and trans-2-octene, and the biomass-derived olefins dl-limonene, α-pinene and methyl oleate.
- Bruno, Sofia M.,Nogueira, Lucie S.,Gomes, Ana C.,Valente, Anabela A.,Gon?alves, Isabel S.,Pillinger, Martyn
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p. 16483 - 16492
(2018/10/24)
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- Titanium-silica catalyst derived from defined metallic titanium cluster precursor: Synthesis and catalytic properties in selective oxidations
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A class of titanium-grafted mesoporous silica catalysts has been designed and prepared starting from molecularly defined metal clusters. The organosol mixture of zerovalent Ti13 clusters was impregnated onto the surface of ordered mesoporous silica molecular sieves (MCM-41 and MMM-2) and, after high-temperature calcination, an evenly dispersed non-single-site Ti(IV)nOx-like silica-supported catalyst was obtained. The catalytic solids, fully characterized by microscopic, spectroscopic and porosimetric techniques, showed standard performance in the liquid-phase epoxidation of a cyclic alkene, as limonene, but remarkably high selectivity values in the oxidative carboxylation of styrene, with tert-butylhydroperoxide and carbon dioxide in the presence of tetrabutylammonium bromide as a cocatalyst. Unprecedented high yields, up to 67%, in styrene carbonate were achieved after 24 h, under solvent-free conditions. The catalysts displayed also a noteworthy stability of the performance to repeated recovery and reuse cycles.
- Evangelisti, Claudio,Guidotti, Matteo,Tiozzo, Cristina,Psaro, Rinaldo,Maksimchuk, Nataliya,Ivanchikova, Irina,Shmakov, Alexandr N.,Kholdeeva, Oxana
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p. 393 - 401
(2017/10/05)
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- Ionic ammonium and anilinium based polymolybdate hybrid catalysts for olefin epoxidation
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Ionic polymolybdate hybrids (IPH) are interesting catalysts for liquid phase olefin epoxidation with tert-butylhydroperoxide; (tbhp), e.g. conversion of terpenic and fatty acid methyl ester (FAME) components of biomass to useful bio-products. IPHs may be easily prepared, under clean, mild, aqueous phase conditions. The type of organic precursor and the synthesis conditions influence the structural features of the IPHs. In this work, IPH epoxidation catalysts possessing one- (1-D) or two-dimensional (2-D) structures were investigated, which included the new materials 1-D methylammonium ammonium trimolybdate [Mo3O10?CH3NH3·NH4] (1) and 2-D bis(2,5-dimethylanilinium) pentamolybdate [Mo5O16?2(NH3C6H3(CH3)2)] (4) with solved structures, and 1-D bis(3,5-dimethylanilinium) trimolybdate [Mo3O10·2(NH3C6H3(CH3)2)] (2), bis(4-methylanilinium) trimolybdate [Mo3O10·2(NH3C6H4CH3)] (3), 2-D bis(anilinium) pentamolybdate [Mo5O16?2(NH3C6H5)] (5), bis(4-methylanilinium) pentamolybdate [Mo5O16?2(NH3C6H4CH3)] (6) and bis(4-ethylanilinium) pentamolybdate [Mo5O16?2(NH3C6H4C2H5)] (7). Systematic characterisation and catalytic studies helped gain insights into structure-activity relationships. The best-performing catalyst (2) was effective for the epoxidation of the FAMEs such as, methyl oleate which gave 92% methyl 9,10-epoxyoctadecanoate yield, at 99% conversion, at 70 °C. The reaction conditions (temperature, type of cosolvent and oxidant) influenced the catalytic reaction. Catalytic performance in consecutive batch runs was steady, and the structural features were essentially preserved.
- Bo?ek, Barbara,Neves, Patrícia,?asocha, Wies?aw,Valente, Anabela A.
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- Hydrogen bond donor functionalized dioxido-molybdenum(VI) complexes as robust and highly efficient precatalysts for alkene epoxidation
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The synthesis of four novel, tridentate aminophenolate ligands HL1-HL4, bearing amide functionalities is reported. Reaction of these ligands with a dioxido molybdenum(VI) precursor led, depending on the choice of solvent, to mononuclear complexes of the type [MoO2L(OMe)] (2, 4, 6) or dinuclear complexes [{MoO2L}2(μ-O)] (1, 3, 5, 7), containing one facially, tridentate ONO-ligand per metal center. This synthetic discrimination between dinuclear and mononuclear complexes allows for a comparison between structures and reactivity. Complexes 1-7 were found to be highly active catalysts in the epoxidation of several internal and terminal alkenes. With tert-butyl hydroperoxide (TBHP) as oxidant, precatalyst loadings of 0.0005 mol% (5 ppm) could be realized leading to turnover numbers of up to 110000. The precatalysts also allowed for the use of hydrogen peroxide (0.1 mol% precatalyst) as oxidant as well as various alcohols as “green” solvents, such as ethanol or even tert-butanol (usually an inhibitor of epoxidation).
- Zwettler, Niklas,Schachner, J?rg A.,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
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p. 209 - 219
(2017/11/15)
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- Chemistry and Catalytic Performance of Pyridyl-Benzimidazole Oxidomolybdenum(VI) Compounds in (Bio)Olefin Epoxidation
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The chemistry and catalytic performance of the dichlorido complex [MoO2Cl2(pbim)] (1) [pbim = 2-(2-pyridyl)-benzimidazole] in the epoxidation of olefins is reported. Complex 1 acts as a precatalyst and is more effective with tert-butylhydroperoxide (TBHP) as the oxidant than with aq. hydrogen peroxide: the cis-cyclooctene (Cy) reaction with TBHP gave 98 % epoxide yield at 70 °C/24 h. Catalyst characterization showed that 1 is transformed in situ to the oxidodiperoxido complex [MoO(O2)2(pbim)] (2), with H2O2 and a hybrid molybdenum(VI) oxide solid formulated as [MoO3(pbim)] (3) with TBHP. The hybrid material 3 was prepared on a larger scale and explored for the epoxidation of the biorenewable olefins methyl oleate, methyl linoleate, and (R)-(+)-limonene. With TBHP as the oxidant, 3 acts as a source of soluble active species of the type 2. A practical method for recycling oxidodiperoxidomolybdenum(VI) catalysts for the Cy/TBHP reaction is demonstrated by using an ionic liquid as the solvent for the molecular catalyst 2.
- Neves, Patrícia,Nogueira, Lucie S.,Gomes, Ana C.,Oliveira, Tania S. M.,Lopes, André D.,Valente, Anabela A.,Gon?alves, Isabel S.,Pillinger, Martyn
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p. 2617 - 2627
(2017/05/29)
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- Catalytic homogeneous oxidation of monoterpenes and cyclooctene with hydrogen peroxide in the presence of sandwich-type tungstophosphates [M4(H2O)2(PW9O34)2]n?, M = CoII, MnII and FeIII
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Catalytic efficiency of tetrabutylammonium salts of sandwich tungstophosphates B‐α‐[M4(H2O)2(PW9O34)2]n?, M = CoII, MnII, FeIII, was studied in the oxidation of (R)-(+)-limonene, geraniol, linalool, linalyl acetate, carveol, and cis-cyclooctene with hydrogen peroxide, in acetonitrile. Oxidation of (R)-(+)-limonene gave limonene-1,2-diol as main product. Epoxidation of linalool takes place preferentially at the more substituted 6,7-double bond, the corresponding 6,7-epoxide reacting further, yielding furano- and pyrano-oxides, via intramolecular cyclization. Oxidation of linalyl acetate occurred preferentially at the more substituted 6,7-double bond for Mn4(PW9)2, affording 6,7-epoxide at 82% selectivity. Linalyl acetate 1,2-epoxide was the major product with 51% and 77% selectivity for Co4(PW9)2 and Fe4(PW9)2, respectively. Oxidation of carveol occurred with very good conversions in the presence of Mn4(PW9)2, Co4(PW9)2 and Fe4(PW9)2, yielding carvone and carveol 1,2-epoxide in similar amounts. Oxidation of cis-cyclooctene gave only the epoxide, while oxidation of geraniol at room temperature afforded 2,3-epoxygeraniol as the major product.
- Santos, Isabel C.M.S.,Gamelas, José A.F.,Duarte, Tiago A.G.,Sim?es, Mário M.Q.,Neves, M. Gra?a P.M.S.,Cavaleiro, José A.S.,Cavaleiro, Ana M.V.
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p. 593 - 599
(2016/12/16)
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- Synthesis, characterization and catalytic application of a new organometallic oligomer based on polyhedral oligomeric silsesquioxane
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Although homogeneous catalysts provide high performance and selectivity, the difficulty of separation and recycling of these catalysts has bothered the scientific community worldwide. Therefore, the demand for heterogeneous catalysts that possess the advantages of homogeneous ones, with ease of separation and recyclability remains a topic of major impact. The oligomeric catalyst synthesized in this work was characterized using elemental analysis, Fourier transform infrared, 13C NMR, 29Si NMR and energy-dispersive X-ray spectroscopies, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer–Emmett–Teller analysis and compared to its homogeneous counterpart [W(CO)3Br2(ATC)] in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene. The results showed that the percentage conversion for the homogeneous species [W(CO)3Br2(ATC)] was slightly higher than for the oligomeric catalyst (POSS-ATC-[W(CO)3Br2]). Furthermore, the selectivity for epoxide of the oligomeric catalyst was greater than that of the homogeneous catalyst by about 25% when (S)-limonene was used. Great conversions (yields) of products were obtained with a wide range of substrates and the catalyst was recycled many times without any substantial loss of its catalytic activity.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Junior, Enes Furlani,Dias Filho, Newton Luiz
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- Zeolite Y encaged Ru(III) and Fe(III) complexes for oxidation of styrene, cyclohexene, limonene, and α-pinene: An eye-catching impact of H2SO4 on product selectivity
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A novel Ru(III) and Fe(III) complexes of ligands 1 and/or 2 {where 1 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol and 2 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene)) bis(4-nitrophenol)} have been synthesized as ‘neat’ and zeolite Y encapsulated complexes. These catalysts are characterized by various analytical tools such as FTIR, UV–vis, elemental analysis, ICP-AES, molar conductivity, 1H- and 13C NMR, TGA, SEM, AAS, BET, magnetic susceptibility and powder XRD to endorse the complex formation, absence of peripheral redundant ligands and complexes, conservation of zeolite Y morphology and crystallinity, and the encapsulation of complexes without devastation in the zeolite Y framework. Out of these synthesized catalysts, 5Y is found to be a potent candidate for styrene (Conv. 76.1%, TOF: 2130 h?1), cyclohexene (Conv. 84.4%, TOF: 2351 h?1), limonene (Conv. 81.6%, TOF: 2273 h?1), and α-pinene (Conv. 72.6%, TOF: 2023 h?1) oxidation with high selectivity of respective allylic products excluding the styrene oxidation, which undergoes epoxidation only. The addition of H2SO4 in an identical reaction catalyzed by 5Y not only surge the conversion up to 100% in a short time span with high TOF but also increase the selectivity of respective epoxidation products. This switchover in the selectivities could be credited to the presence of H2SO4 that facilitates the heterolytic [sbnd]O[sbnd]O[sbnd] bond cleavage of metal hydroperoxide and stimulates the epoxidation over allylic oxidation. Furthermore, the results establish that the heterogeneous systems are effortlessly recovered and reused without ample drop in the activity and selectivity.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
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p. 223 - 237
(2016/12/09)
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- Towards a global greener process: from solvent-less synthesis of molybdenum(vi) ONO Schiff base complexes to catalyzed olefin epoxidation under organic-solvent-free conditions
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Nine Schiff base ligands derived from o-hydroxyaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 2-hydroxy- 1-naphthaldehyde) and nine corresponding dioxomolybdenum(vi) complexes, cis-[MoO2L(CH3OH)] or cis-[MoO2L(CH3OH)]·CH3OH and dinuclear [MoO2L]2, have been prepared using the conventional solution-based method as well as mechanochemically, by liquid assisted grinding (LAG). All products have been characterised by means of IR spectroscopy, thermal analyses and also by powder and five molybdenum complexes by single crystal X-ray diffraction. The crystal structure analysis of mononuclear complexes reveal distorted octahedral Mo(vi) coordination by ONO donor atoms from a dianionic tridentate Schiff base ligand, two oxido oxygen atoms from the MoO22+ moiety and an oxygen atom from the MeOH molecule trans to the oxido oxygen atom. Due to the trans effect of the oxido oxygen atom, Mo-O(MeOH) is the longest bond distance within the Mo coordination sphere and it expected to be the point of maximum reactivity of the complexes. All complexes have been studied as pre(catalysts) for the epoxidation of cis-cyclooctene, cyclohexene and (R)-limonene using aqueous tert-butyl peroxide (TBHP) as the oxidant and in the absence of an organic solvent.
- Cindri?, Marina,Pavlovi?, Gordana,Katava, Robert,Agustin, Dominique
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p. 594 - 602
(2017/02/05)
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- Activated vs. pyrolytic carbon as support matrix for chemical functionalization: Efficient heterogeneous non-heme Mn(II) catalysts for alkene oxidation with H2O2
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Two types of heterogeneous catalytic materials, MnII-L3imid@Cox and MnII-L3imid@PCox, have been synthesized and compared by covalent grafting of a catalytically active [MnII-L3imid] complex on the surface of an oxidized activated carbon (Cox) and an oxidized pyrolytic carbon from recycled-tire char (PCox). Both hybrids are non-porous bearing graphitic layers intermixed with disordered sp2/sp3 carbon units. Raman spectra show that (ID/IG)activatedcarbon > (ID/IG)pyrolyticcarbon revealing that oxidized activated carbon(Cox) is less graphitized than oxidized pyrolytic carbon (PCox). The MnII-L3imid@Cox and MnII-L3imid@PCox catalysts were evaluated for alkene oxidation with H2O2 in the presence of CH3COONH4. Both showed high selectivity towards epoxides and comparing the achieved yields and TONs, they appear equivalent. However, MnII-L3imid@PCox catalyst is kinetically faster than the MnII-L3imid@Cox (accomplishing the catalytic runs in 1.5 h vs. 5 h). Thus, despite the similarity in TONs MnII-L3imid@PCox achieved extremely higher TOFs vs. MnII-L3imid@Cox. Intriguingly, in terms of recyclability, MnII-L3imid@Cox could be reused for a 2th run showing a ～20% loss of its catalytic activity, while MnII-L3imid@PCox practically no recyclable. This phenomenon is discussed in a mechanistic context; interlinking oxidative destruction of the Mn-complex with high TOFs for MnII-L3imid@PCox, while the low-TOFs of MnII-L3imid@Cox are preventive for the oxidative destruction of the Mn-complex.
- Simaioforidou,Papastergiou,Margellou,Petrakis,Louloudi
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p. 516 - 525
(2016/12/16)
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- Mn-Schiff base modified MCM-41, SBA-15 and CMK-3 NMs as single-site heterogeneous catalysts: Alkene epoxidation with H2O2 incorporation
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The development of new functional catalytic materials prepared via appropriate chemical modification of mesoporous silica SBA-15, MCM-41 or carbon nanomaterials CMK-3, are presented. Their synthesis has been carried out via two synthetic approaches: (a) a two steps procedure which includes grafting of the Schiff base ligand 1,3-bis[3-aza-3-(1-methyl-3-oxobut-1-enyl)-prop-3-en-1-yl]-2-(4-hydroxy-phenyl)-1,3-imidazolidine (L) onto the suppors and subsequent metalation of the so-formed hybrid material, and (b) an one step procedure which allows covalent grafting of the entire [MnII-Schiff base] catalyst onto the carbonaceous support. The resulting single-site heterogeneous catalysts were characterized and evaluated for alkene epoxidation with H2O2 in the presence of CH3COONH4 as additive. They are efficient and selective towards formation of epoxides. The highest TONs have been achieved by L@MCM-41-MnII and MnII-L@CMK-3. Moreover, MnII-L@CMK-3 is operative for a second use and kinetically very fast, demonstrating remarkably high TOFs 65-634 h-1 that is correlated to its practically zero porosity. Based on the present data, the textural features of the obtained catalysts are discussed in correlation with their catalytic performance.
- Mavrogiorgou,Baikousi,Costas,Mouzourakis,Deligiannakis,Karakassides,Louloudi
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- Regioselective Organocatalytic Formation of Carbamates from Substituted Cyclic Carbonates
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A highly regioselective catalytic approach has been developed towards carbamates derived from cyclic organic carbonates by reaction of the latter with amine reagents under organocatalytic control. For various combinations of carbonate and amine substrates, an organocatalyst (TBD: 1,5,7-triazabicyclo[4.4.0]dec-5-ene) was used to increase the reaction kinetics while exerting excellent regioselective control. The current method is the first general approach towards the control over the regioselectivity of this reaction using a wide variety of easily accessed substituted organic carbonates. (Figure presented.) .
- Sope?a, Sergio,Laserna, Victor,Guo, Wusheng,Martin, Eddy,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
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supporting information
p. 2172 - 2178
(2016/07/16)
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